n. a disturbance in the normal fluency and time sequencing of speech. It is characterized by frequent repetition or prolongation of sounds, syllables, or words, with hesitations and pauses that disrupt speech. 

The disorder interferes with one’s ability to communicate with others, especially during stressful situations (e.g., public speaking), and it can be exacerbated by one’s awareness of and anxiety over the dysfluency. The struggle to speak may also be accompanied by behaviors such a rapid eye blinking, trembling lips, or fist clenching. By contrast, speaking in unison with another person, reading orally, or singing may temporarily reduce stuttering. The disorder affects about 1% of all children, with onset occurring between 2 and 7 years of age. Mild cases usually recover spontaneously by the age of 16, but more severe cases may persist into adulthood. In formal diagnostic nomenclature, stuttering is the term used in DSM–IV–TR; it is identified as childhood-onset fluency disorder in DSM–5. Also called stammering. See also primary stuttering; secondary stuttering. Compare cluttering. —stutter vb., n.