from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A word or form that occurs only once in the recorded corpus of a given language.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A word occurring only once in a given corpus.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a word with a special meaning used for a special occasion
Greek : hapax, once + legomenon, neuter sing. passive participle of legein, to count, say.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Ancient Greek ἅπαξ λεγόμενον ("(something) said only once"). (Wiktionary)