From Wiktionary, the free dictionary
So called from being written with a slash, such as Em/G (E minor with a G bass).
slash chord (plural slash chords)
- (music) A chord which has a bass note that is not the root note.
1986, Michael Esterowitz, How to Play from a Fake Book, Ekay Music, →ISBN, page 34:Contemporary popular music tends to be specific in indicating slash cords, while older fake books generally indicate only root chord names.