any of several annual or perennial Eurasian grasses

Ryegrass (Lolium) is a genus of nine species of tufted grasses, family Poaceae. Also called tares, these plants are native to Europe, Asia and northern Africa, but are widely cultivated and naturalised elsewhere. Ryegrasses are naturally diploid, with 2n = 14, and are closely related to the fescues Festuca.