bluegrass

Short definition from Wiktionary

Noun

1. 1
   Kentucky bluegrass, Poa pratensis.
2. 2
   A subgenre of country music with roots in Scots-Irish Appalachian folk music, blues, and jazz and characterized by banjos, fiddles, acoustic guitars, dobros, and mandolins; but containing no drums, electric guitars, pianos or other keyboard or wind instruments; using a bass fiddle to carry its rhythm.