rhombus n. + Add to list UK //ɹˈɒmbəs// rhom·bus Archaic SynonymsEtymology Synonyms diamondrhombOriginGRKῥόμβος→ENrhombus Learned borrowing from Latin rhombus, from Ancient Greek ῥόμβος (rhómbos, “rhombus, spinning top”). Doublet of rhomb and rhumb.