From Longman Dictionary of Contemporary Englishcrabgrasscrab‧grass /ˈkræbɡrɑːs $ -ɡræs/ noun [uncountable] American English HBPa kind of rough grass
Examples from the Corpus
crabgrass• In my case, before becoming a Snavely winner, I was but crabgrass in the Garden of Physics.• Because the boomerang is like crabgrass, Tom Arnold and Strom Thurmond, it keeps coming back. 