Grass  —n. 1 a any of a group of wild plants with green blades that are eaten by ruminants. B plant of the family which includes cereals, reeds, and bamboos. 2 pasture land. 3 grass-covered ground, lawn. 4 grazing (out to grass). 5 slang marijuana. 6 slang informer. —v. 1 cover with turf. 2 us provide with pasture. 3 slang a betray, esp. To the police. B inform the police.  grassy adj. (-ier, -iest). [old english]