1. Mentioning something by saying it will not be mentioned.
2. The rhetorical device of alluding to something by denying that it will be mentioned, as in "I won't bring up the question of age now that you are seventy."
3. The denial of someone's intention to talk about a subject that is at the same time named or insinuated; such as, “I shall not mention Caesar's avarice, nor his cunning, nor his morality.”