Lewis Short
irrīsĭo | inr- (noun F) : (), , id.
* A deriding, mocking, mockery: liber a tali irrisione Socrates,Cic. Ac. 2, 39, 123: stultitiae,Auct. Her. 1, 6, 10: irrisio omnium,Cic. de Or. 1, 12, 50: cum irrisione audientium,id. de Off. 1, 38, 137.
Charlton T. Lewis, Charles Short, A Latin Dictionary