[fifth] n, pl fifths (bef. 12c) 1: one that is number five in a countable series
2. a: the musical interval embracing five diatonic degrees b: a tone at this interval; specif: dominant 1 c: the harmonic combination of two tones at this interval
3: a unit of measure for liquor equal to one fifth of a U.S. gallon (0.757 liter)
4. cap: the Fifth Amendment of the U.S. Constitution -- fifth adj or adv -- fifth.ly adv