A heterogram (from hetero-, meaning "different", + -gram, meaning
"written") is a word, phrase, or sentence in which no letter of the
alphabet occurs more than once.
As you ask for the name of a property and heterogram refers to the word (or phrase or sentence) itself, you could say that a word is heterogrammatic.
Words related to heterogram include:
- pangram, a word or phrase containing all the letters of the alphabet; and
- isogram, a word or phrase in which all letters occur an equal number of times
There's room for overlap in these categories, of course.
As the Wikipedia article notes:
An isogram ... is the same as a heterogram when each letter occurs once. ...
A perfect heterogram is ... the same as a perfect pangram, since both consist of all letters of the alphabet with each represented exactly once.
The word heterogram does not have particularly wide currency, presumably as it is so specific and specialist, and most dictionaries do not seem to list it. (I've come across it before but I only find it in Wiktionary and in Wikipedia; I don't have proper paper dictionaries to hand at the moment to check.)
Alternative definitions of heterogram
To further complicate matters, while heterogram does fit the bill here, it also has several additional definitions.
A heterogram can also be:
in the study of ancient texts ... a special kind of a logogram consisting of the embedded written representation of a word in a foreign language, which does not have a spoken counterpart in the main ... language of the text.
[For example] in English, the written abbreviations e.g., i.e., and viz. are often read respectively as "for example", "that is", and "namely".
And also, apparently:
a heterogram is a poem in which no two adjacent words share a letter in common.
I'm not sure about this last definition; it sounds familiar to me but I can't find it attested to elsewhere. Perhaps take it with a pinch of salt.