suspended chord
A chord where the third is replaced by a second or fourth, creating an unresolved, ambiguous quality.
In Depth
Suspended chords (sus2 and sus4) eliminate the major or minor third that defines a chord's quality, replacing it with a note that wants to resolve. Sus4 chords are the more common type, with the fourth pulling toward the third like a gentle tension. In pop and rock, sus chords create beautiful moments of anticipation before resolving. In jazz, sus chords are used as harmonic colours in their own right. Pete Townshend of the Who built an entire guitar style around sus chords.
The opening chord of A Hard Day's Night by the Beatles has been debated for decades; analysis reveals it contains a suspended element that gives it its uniquely ambiguous, jangling quality.