Definition of "Grain" :

noun: the physical composition of something (especially with respect to the size and shape of the small constituents of a substance)

"Sand of a fine grain."

noun: the direction, texture, or pattern of fibers found in wood or leather or stone or in a woven fabric

"Saw the board across the grain."

noun: the smallest possible unit of anything

"There was a grain of truth in what he said."

noun: foodstuff prepared from the starchy grains of cereal grasses

noun: a relatively small granular particle of a substance

"A grain of sand."

noun: a cereal grass

"Wheat is a grain that is grown in Kansas."

noun: dry seed-like fruit produced by the cereal grasses: e.g. wheat, barley, Indian corn

noun: 1/7000 pound; equals a troy grain or 64.799 milligrams

noun: 1/60 dram; equals an avoirdupois grain or 64.799 milligrams

noun: a weight unit used for pearls or diamonds: 50 mg or 1/4 carat

noun: the side of leather from which the hair has been removed

verb: become granular

verb: form into grains

verb: paint (a surface) to make it look like stone or wood

verb: thoroughly work in

"His hands were grained with dirt."