you are trying to get somebody's attention by waving your hand or saying hello! but he or she ignores you; I am looking for an Idiom or word to describe the situation or attitude of that person.
That person has "snubbed" you.
P.S. To snub a person is to ignore the person intentionally, motivated by a belief in and a desire to express one's own superiority, which belief can be founded on wealth, power, social class, intellectual endowments, physical beauty, or moral self-righteousness, among other things.
As user myol remarks, there are socially awkward people who may only seem to be snubbing others, when in actuality they lack the temperament to engage socially or they do not know how to "read" facial expressions and understand "body language".
They gave you the cold shoulder.
If a Yank may be permitted to invoke what I think is distinctly British slang, maybe even specifically English, I would suggest the verb cut:
- colloq. a. trans. To break off acquaintance or connection with (a person); also (as a single act) to affect not to see or know (a person) on meeting or passing him. Often emphasized by dead. [OED]
Perhaps others can comment on the currency of this usage, or lack thereof, in other parts of the archipelago and former empire. But I know that American readers tend to require explanation of British usage of both cut and joint in order to fathom one of Lewis Carroll’s jokes in Chapter IX of Through the Looking-Glass.
Here is an example of this usage of cut, as requested, from Bernard Shaw’s Pygmalion, Act II:
LIZA. I should just like to take a taxi to the corner of Tottenham Court Road and get out there and tell it to wait for me, just to put the girls in their place a bit. I wouldnt speak to them, you know.
PICKERING. Better wait til we get you something really fashionable.
HIGGINS. Besides, you shouldnt cut your old friends now that you have risen in the world. Thats what we call snobbery.
There is an example of the usage as emphasized with dead here.
Perhaps the most neutral term would be disregard.
Despite my signals, I was disregarded.
If a sense of duty is involved, neglect might also be appropriate.
The soldiers neglected all the protestations of the medical staff.
You could also say that the person did not acknowledge you, or refused to acknowledge you.
I tried to attract his attention at the other side of the party by calling his name and waving, but he didn't acknowledge me.
A slightly different nuance can be provided by using recognize, instead.
After the incident at the wedding reception, the bride's side of the family refused to recognize the best man.
ac·knowl·edge əkˈnäləj/ verb verb: acknowledge; 3rd person present: acknowledges; past tense: acknowledged; past participle: acknowledged; gerund or present participle: acknowledging
1. accept or admit the existence or truth of. "the plight of the refugees was acknowledged by the authorities" synonyms: admit, accept, grant, allow, concede, accede to, confess, own, recognize "the government acknowledged the need to begin talks" antonyms: reject, deny 2. (of a body of opinion) recognize the fact or importance or quality of. "the art world has begun to acknowledge his genius" express or display gratitude for or appreciation of. "he received a letter acknowledging his services" synonyms: express gratitude for, show appreciation for, thank someone for "Douglas was glad to acknowledge her help" accept the validity or legitimacy of. "Henry acknowledged Richard as his heir" synonyms: recognized, accepted, approved, accredited, confirmed, declared, confessed, avowed "the acknowledged leader of the neo-Impressionist movement" 3. show that one has noticed or recognized (someone) by making a gesture or greeting. "she refused to acknowledge my presence" synonyms: greet, salute, address; More nod to, wave to, raise one's hat to, say hello to "he did not acknowledge Colin, but hurried past" antonyms: ignore confirm (receipt of something). synonyms: answer, reply to, respond to "nobody acknowledged my letters" antonyms: overlook
Origin late 15th century: from the obsolete Middle English verb knowledge, influenced by obsolete acknow ‘acknowledge, confess.’
rec·og·nize ˈrekəɡˌnīz/ verb verb: recognize; 3rd person present: recognizes; past tense: recognized; past participle: recognized; gerund or present participle: recognizing; verb: recognise; 3rd person present: recognises; past tense: recognised; past participle: recognised; gerund or present participle: recognising
1. identify (someone or something) from having encountered them before; know again. "I recognized her when her wig fell off" identify from knowledge of appearance or character. "Pat is very good at recognizing wildflowers" synonyms: identify, place, know, put a name to; More remember, recall, recollect; know by sight "Hannah recognized him at once" (of a computer or other machine) automatically identify and respond correctly to (a sound, printed character, etc.). 2. acknowledge the existence, validity, or legality of. "the defense is recognized in Mexican law" synonyms: acknowledge, accept, admit; More realize, be aware of, be conscious of, perceive, discern, appreciate; formalbe cognizant of "they recognized Alan's ability" officially approve, certify, accredit, endorse, sanction, validate "psychotherapists who are recognized" officially regard (a qualification) as valid or proper. "these qualifications are recognized by the Department of Education" grant diplomatic recognition to (a country or government). "they were refusing to recognize the puppet regime" show official appreciation of; reward formally. "his work was recognized by an honorary degree from Georgetown University" synonyms: pay tribute to, show appreciation of/for, appreciate, be grateful for, acclaim, commend "the board recognized their hard work" (of a person presiding at a meeting or debate) call on (someone) to speak.
Origin late Middle English (earliest attested as a term in Scots law): from Old French reconniss-, stem of reconnaistre, from Latin recognoscere ‘know again, recall to mind,’ from re- ‘again’ + cognoscere ‘learn.’
Sounds to me like a clear example of "Nelsonian blindness".
Before the Battle of Copenhagen, Nelson famously clapped his telescope to his blind eye and declared that he could not see the signal demanding his withdrawal.
(The phrase is now also used as a term of English law in order to denote the dishonesty of one who deliberately refrains from making the enquiries which an honest person would make.)
Perhaps a colloquial term in the UK, it is similar to Snubbed but IMHO has less negative connotations.
When 'snubbed', generally the person is in a social situation where ignoring you gives them greater benefit than acknowledging you. This is generally seen as malicious, as they are pretending not to have any connection to you or simply do not wish to interact with you.
When 'blanked' the person can be doing it for malicious reasons or they can simply be in their own head. They could have heard some tragic news in a separate conversation and be trying to keep a straight face. They could appear to be looking toward you from the other-side of the room but be actually be daydreaming.
Some times it can be easier to 'blank' someone to try and limit the number of things we have to simultaneously deal with. Or sometimes we simply space out.
I don't know what's up with Kara, she just blanked me for no reason.
If you are sure the person is doing it on purpose and to exclude you from a social group, then I feel the most appropriate word for excluding you from a group is;
Wow did you see that? James just ostracized me in front of everyone for no reason.
That person is being supercilious; from en.wiktionary, with emphasis added, it means
Arrogantly superior; showing contemptuous indifference; haughty.
One might also say they are giving you the silent treatment, which from en.wiktionary is
A form of social sanction that consists of ignoring a particular individual, neither speaking to that person nor responding to his or her words.
or that they have sent you to Coventry. Of the phrase, en.wikipedia says
To send someone to Coventry is a British idiom meaning to deliberately ostracise someone. Typically, this is done by not talking to them, avoiding their company and generally pretending that they no longer exist. Victims are treated as though they are completely invisible and inaudible.
There is also pied in slang.
Wow that guy totally pied you!
When you try to make your presence known to someone by waving or nodding, the the recipient either ignores or does not realise. You have just been pied. This is the perfect time for a friend to suggest that you wipe your face, because it's covered in pie.