Source : Webster's Revised Unabridged Dictionary (1913)

Rhombus \Rhom"bus\, n. [L.]
   Same as {Rhomb}, 1.

Source : WordNet®

rhombus
     n : a parallelogram with four equal sides; an oblique-angled
         equilateral parallelogram [syn: {rhomb}]
     [also: {rhombi} (pl)]