Real Dictionary

grass
singular noun: If you talk about the grass, you are referring to an area of ground that is covered with grass, for example in your garden.
variable noun: Grass is a very common plant consisting of large numbers of thin, spiky, green leaves that cover the surface of the ground.

Grass in American English
ˈGünter (Wilhelm) (ˈgyntɛʀ) ; E ˈguntər ) 1927- ; Ger. writer
any of various plants of the grass family that are usually used for food, fodder, or grazing and as lawns
designating a family (Poaceae, order Cyperales) of monocotyledonous plants with long, narrow leaves, jointed stems, flowers in spikelets, and seedlike fruit, including wheat, rye, barley, oats, corn, sugar cane, bamboo, sorghum, and bluegrass
to become covered with grass
to put (an animal or animals) out to pasture or graze
noun: any plant of the family Gramineae, having jointed stems, sheathing leaves, and seedlike grains

grass in British English
noun: any monocotyledonous plant of the family Poaceae (formerly Gramineae), having jointed stems sheathed by long narrow leaves, flowers in spikes, and seedlike fruits. The family includes cereals, bamboo, etc
noun: Günter (Wilhelm) (ˈɡyntər ). 1927–2015, German novelist, dramatist, and poet. His novels include The Tin Drum (1959), Dog Years (1963), The Rat (1986), Crabwalk (2002), and Peeling the Onion (2007). Nobel prize for literature 1999