Usually said in a situation when the rule is incorrect and unusable.

(programming) An exception (error condition) when handled by a debugger, such that the programmer has the first chance to study it; such an exception would otherwise proceed to a handler or (in its absence) crash the program.

plural of first-chance exception

(grammar) A phenomenon where the subject of an embedded infinitival verb seems to appear in the superordinate clause, and, if a pronoun, is unexpectedly marked with objective case morphology.

plural of exception that proves the rule

plural of exception that proves the rule

Alternative form of there is an exception to every rule

(idiomatic) These negative remarks do not pertain to anyone who is currently listening to them (including the speaker).

Alternative letter-case form of I before E, except after C

(orthography, mnemonic) In English words that contain the letters I and E together, the I tends to come before the E (ie), except in cases when the two are preceded by the letter C, in which case the E comes before the I (cei).