Tic
A tic is a sudden, repetitive, nonrhythmic motor movement or vocalization involving discrete muscle groups. Tics can be invisible to the observer, such as abdominal tensing or toe crunching. Common motor and phonic tics are, respectively, eye blinking and throat clearing.
Tic
A simple phonic tic can be almost any sound or noise, with common vocal tics being throat clearing, sniffing, or grunting.