definition rhombus
Wiktionary (0.00 / 0 votes) Rate this definition: rhombus (Noun). Any of several flatfishes once considered part of the genus Rhombus. rhombus (Noun). A parallelogram having all sides of equal length. Origin: From rhombus, from á¿¥ÏÎ¼Î²Î¿Ï, from á¿¥Î­Î¼Î²Ï.