rhombus

noun, plural rhom·bus·es, rhom·bi [rom-bahy] /ˈrɒm baɪ/.

1. an oblique-angled equilateral parallelogram; any equilateral parallelogram except a square.
2. an equilateral parallelogram, including the square as a special case.
3. a rhombohedron.

noun plural -buses or -bi (-baɪ)

1. an oblique-angled parallelogram having four equal sidesAlso called: rhomb Compare square (def. 1)

n.

1560s, from Late Latin rhombus, from Greek rhombos “rhombus, rhomb, lozenge; spinning top, maghic wheel used by sorcerers; a spinning motion,” from rhembesthai “to spin, whirl,” from PIE *wrembh-, from *werbh- “to turn, twist, bend” (cf. Old English weorpan “to throw away”), from root *wer- (3) “to turn, bend” (see versus).

Plural rhombuses rhombi (rŏm′bī)

1. A parallelogram with four equal sides; an equilateral parallelogram.