rhombus

water caltrop (Trapa species), aquatic plant with edible seeds

see 菱花鏡|菱花镜[ling2 hua1 jing4]

antique bronze mirror with flower petal edging, most commonly from the Tang dynasty

magnesite; magnesium ore

Mitsubishi (Japanese conglomerate)

(military) caltrop (spiky metal device laid on the ground to create a hazard for enemy horses or troops in ancient times)

rhombus of Michaelis (anatomy)