Source : Webster's Revised Unabridged Dictionary (1913)

Sinusoid \Si"nus*oid\, n. [Sinus + -oid.] (Geom.)
   The curve whose ordinates are proportional to the sines of
   the abscissas, the equation of the curve being y = a sin x.
   It is also called the {curve of sines}.

Source : WordNet®

sinusoid
     n 1: tiny endothelium-lined passages for blood in the tissue of
          an organ
     2: the curve of y=sin x [syn: {sine curve}]