Definitions for "Irregular Verb"
a verb that does not add -ed to form the past tense
a verb which does not conform to an expected inflectional pattern, derivation, or word formation
A verb that forms the simple past in a different way than regular verbs. Some irregular verbs use the simple form as their simple past and past participle form (put put - put); others have one irregular form for both the simple past and the past participle (buy - bought - bought); and others have different simple past and past participle forms (sing - sang - sung).