rhombus

Noun

rhombus (plural rhombi or rhombuses)

1. A parallelogram having all sides of equal length.
   1. The rhombus diamond, as one of the suits seen in a deck of playing cards ( or ).
2. In early Greek religion, an instrument whirled on the end of a string similar to a bullroarer.
   • The Greeks also used an instrument called a rhombus, or witches' wheel. As the wheel spun round, it was thought that influence was gained over certain people or circumstances.1936, Rollo Ahmed, The Black Art, London: Long, page 58
3. (archaic) Any of several flatfishes, including the brill and turbot, once considered part of the genus Rhombus, now in Scophthalmus.
   • the greedy Tuberon or Shark arm'd with a double row of venemous teeth pursues them, directed by a little Rhombus, Musculus or pilot-fish that scuds to and fro to bring intelligence [...].1638, Thomas Herbert, Some Yeares Travels, section I
4. (archaic) Snails, now in genus Conus or family Conidae.