bird grass

noun
  1. a grass, Poa trivialis, grown in temperate regions of North America largely for lawns and turf.
  2. the knotgrass, Polygonum aviculare.

Origin of bird grass

An Americanism dating back to 1775–85
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018