stammer

American Heritage® Dictionary of the English Language, Fourth Edition

1. v. To speak with involuntary pauses or repetitions.
2. v. To utter with involuntary pauses or repetitions.
3. n. A way of speaking characterized by involuntary pauses or repetitions.

Century Dictionary and Cyclopedia

1. To hesitate or falter in speaking; hence, to speak with involuntary breaks and pauses.
2. To stumble or stagger.
3. Synonyms Falter, Stammer, Stutter. He who falters weakens or breaks more or less completely in utterance; the act is occasional, not habitual, and for reasons that are primarily moral, belong to the occasion, and may be various. He who stammers has great difficulty in uttering anything; the act may be occasional or habitual; the cause is confusion, shyness, timidity, or actual fear; the result is broken and inarticulate sounds that seem to stick in the mouth, and sometimes complete suppression of voice. He who stutters makes sounds that are not what he desires to make; the act is almost always habitual, especially in its worst forms; the cause is often excitement; the result is a quick repetition of some one sound that is initial in a word that the person desires to utter, as c-c-c-c-catch.
4. To utter or pronounce with hesitation or imperfectly; especially, to utter with involuntary breaks or catches: frequently with out.
5. n. Defective utterance; a stutter: as, to be troubled with a stammer. See stammering.

Wiktionary

1. v. To keep repeating a particular sound involuntarily.
2. n. The involuntary repetition of a sound in speech.

GNU Webster's 1913

1. v. To make involuntary stops in uttering syllables or words; to hesitate or falter in speaking; to speak with stops and difficulty; to stutter.
2. v. To utter or pronounce with hesitation or imperfectly; -- sometimes with out.
3. n. Defective utterance, or involuntary interruption of utterance; a stutter.

WordNet 3.0

1. v. speak haltingly
2. n. a speech disorder involving hesitations and involuntary repetitions of certain sounds