invalidate Copy link Outline 1. infirmo, 1 (to annul; disprove)2. expr. by irrĭtus and a verb3. lăbĕfacto, 1 (to cause to totter; hence, to take away the strength of) • invalidate: 1. infirmo, 1 (to annul; disprove): a contract is i.d, infirmatur contractus, Hermog. Dig. 49, 14, 46 § 2 by repealing one law to i. the rest, unam tollendo legem ceteras i., Liv. 34, 3. to i. and disprove anything, aliquid inf. et tollere, Cic. N. D. 2, 59, 147. 2. expr. by irrĭtus and a verb: to i. laws (annul them), leges irritas facere, Cic. Ph. 5, 7, fin. Join: tollere atque irritum esse jubere, Cic. Verr. 2, 2, 57, init. 3. lăbĕfacto, 1 (to cause to totter; hence, to take away the strength of): to i. an opinion, opinionem l., Cic. Clu. 2, 6: to i. laws, leges ac jura l., Cic. Caec. 25, 70.