An Irish bull, or simply a bull, is a ludicrous language blunder: an illogical, absurd, and/or amusing mistake - especially one that is paradoxical or self-contradictory. Some dictionaries take a casual approach to Irish bulls, defining them but omitting actual examples.
Borgmann, Dmitri A.
Word Ways: Vol. 20
, Article 11.
Available at: http://digitalcommons.butler.edu/wordways/vol20/iss1/11