Source : Webster's Revised Unabridged Dictionary (1913)

Rhomboid \Rhom"boid\ (r[o^]m"boid), n. [Gr. ??? rhomboidal; ???
   rhomb + e'i^dos shape: cf. F. rhombo["i]de.] (Geom.)
   An oblique-angled parallelogram like a rhomb, but having only
   the opposite sides equal, the length and with being
   different.

Rhomboid \Rhom"boid\ (r[o^]m"boid), a.
   Same as {Rhomboidal}.

Source : WordNet®

rhomboid
     n 1: a parallelogram with adjacent sides of unequal lengths; an
          oblique-angled parallelogram with only the opposite
          sides equal
     2: any of several muscles of the upper back that help move the
        shoulder blade [syn: {rhomboid muscle}]

rhomboid
     adj : shaped like a rhombus or rhomboid; "rhomboidal shapes" [syn:
            {rhomboidal}]