If unsolicited bulk mail in your inbox is referred to as spam, what would be its equivalent for someone talking indiscriminately, but face-to-face without the intervention of technology.
There is bend someone's ear:
(idiomatic) To bore; to talk too long, especially to one particular person.
It's like prating, but with a connotation of being unable to politely escape.
The purpose of spam, or junk e-mail, seems to be to get attention, for some reason that can only be discovered by clicking on the e-mail. Teenagers sometimes speak to the entire room, with the apparent hope that someone will pay attention, sometimes with important information, and sometimes not. I think of it as, "Chatter," since it is meant to gain attention, or simply to entertain, without a whole lot of specific content. But one can only really tell what they want by interrupting the chatter, and asking them. In a sense, one must click on the chatter.
I would use the word Rant.
- To speak or write in an angry or emotionally charged manner; rave.
- To express at length a complaint or negative opinion: "He could rant on the subject of physician-assisted illness" (Paul Theroux). v.tr. To utter or express by ranting: "Adams's fellow Federalists ranted that he was mentally unfit to be president" (Susan Dunn). n.
- Angry, emotionally charged, or tediously negative speech or writing: a speech that was more rant than reason.
- An example of such speech or writing: a rant against the university's policies.
If you take spam to be an attempt to get you to buy something that you don't want, then the person doing all the talking is a salesman.
The stream of words used to sell is known as Sales Patter.
I have always understood the phrase to liken the patter of words to the patter of raindrops - meaningless noise.
The phrase is most frequently used in reference to market traders, used car dealers and insurance brokers.