To introduce involuntary repetitions and pauses into one's speech
A speech impediment marked by involuntary repetitions and pauses
In 1861 he was ordained deacon, but he never took priest's orders, possibly because of a stammer which prevented reading aloud.
From these injuries he slowly recovered, but he long continued to stammer in his speech, whence the nickname, adopted by himself, of "Tartaglia."
Does the person stammer over words or seem to lose track of the flow of the conversation?
His professional success was not great; his manner was violent, his appearance unattractive, and his speech impaired by a painful stammer.
conquered most of his problems with speech but retained a stammer for the rest of his life.