1620s, ultimately from Greek kithara "cithara," a stringed musical instrument related to the lyre, perhaps from Persian sihtar (see sitar); the name reached English several times, including early 14c. giterne, in reference to various stringed, guitar-like instruments; the modern word is directly from Spanish guittara, from Arabic qitar, from the Greek.
A stringed musical instrument (see strings) usually played by strumming or plucking. Guitars are widely used in folk music and, often amplified electronically, in country and western music and rock 'n' roll.