[blue.grass] n (1751) 1: any of several grasses (genus Poa) of which some have bluish green culms; esp: kentucky bluegrass
2. [fr. the Blue Grass Boys, performing group, fr. Bluegrass state, nickname of Kentucky]: country music played on unamplified stringed instruments (as banjo, fiddle, guitar, and mandolin) and characterized by free improvisation and close usu. high-pitched harmony