As a verb stammer
is .
As a noun nonfluency is
lack of fluency; some period of nonfluent speech caused by a stammer, etc.
stammer
English
Verb
(
en verb)
To keep repeating a particular sound involuntarily during speech.
Synonyms
* stutter
Noun
(
en noun)
The involuntary repetition of a sound in speech.
nonfluency
English
Noun
Lack of fluency; some period of nonfluent speech caused by a stammer, etc.