madness /ˈmad.nəs/noun 3forms 1phrases 1 noun3 •serious illness of the mind that makes someone think and behave in strange waysThough this be madnesse, / Yet there is Method in 't: […] — 1599 •Rash folly. •The state of being angry. formsmadnesses Phrases with madness method to one's madnessA well-thought-out reason for an individual's seemingly illogical behavior.