nystagmus

from WordNet (r) 3.0 (2006)

nystagmus
    n 1: involuntary movements of the eyeballs; its presence or
         absence is used to diagnose a variety of neurological and
         visual disorders

from The Collaborative International Dictionary of English v.0.48

Nystagmus \Nys*tag"mus\, n. [NL., fr. Gr. ? drowsiness, fr. ? to
   nod in sleep, to slumber.] (Med.)
   A rapid involuntary oscillation of the eyeballs.
   [1913 Webster]

[email protected]