a slang term for a chord that only contains the root and the fifth
a two-note chord, I-V
A chord which contains no 3rd (suspended chords, and chords containing 3 or more notes exempted).
A chord consisting of the first (root), fifth and eighth degree (octave) of the scale. Power chords are typically used in playing rock music.
In rock, punk and metal music, a power chord is a bare fifth, or a similar chord, usually played on electric guitar with distortion.