stammer UK /ˈstæmə/US /ˈstæmɚ/noun 2verb 2forms 5 noun2 •The involuntary repetition of a sound in speech.She said goodbye in a stammer. •A speech defect whereby someone speaks with a stammer verb2 •To keep repeating a particular sound involuntarily during speech. •To utter with a stammer, or with timid hesitancy.He blushed, and stammered a few words of apology. formsstammered · stammering · stammereth · stammers · stammerest