1
general::
A phrase used to fend off questions about a situation one finds awkward, unpleasant, or unsatisfactory. For example, How did we do in the bridge tournament? Don't ask! [Colloquial; 1960s] For a similar phrase, see FORGET IT.
American Heritage Idioms
2
general::
Phrase(s): Don’t ask.
It is so bad, I do not wish to be reminded or talk about it, so do not ask about it. • John: How was your class reunion? Alice: Oh, heavens! Don’t ask. • Tom: What was your calculus final exam like? Mary: Don’t ask.
McGrawhill's American Idioms And Phrasal Verbs