noun
rhythm guitar; backing guitar
Wasei-eigo term used in music contexts to refer to the guitar part that provides rhythmic and harmonic support, as opposed to lead guitar.
wasei-eigo (Japanese-coined English), from side guitar
彼はバンドでサイドギターを担当している。
He plays rhythm guitar in the band.
サイドギターのリフが曲の土台になっている。
The rhythm guitar riff forms the foundation of the song.