bromegrass n any of various woodland and meadow grasses of the genus Bromus; native to temperate regions Usage(s) He studies his cows as they munch on the lush green pasture, a native mix of clover, timothy, orchard and bromegrass. He studies his cows as they munch on the lush green pasture, a native mix of clover, timothy, orchard and bromegrass. Synonym(s) brome