The Collaborative International Dictionary of English v.0.48:
Third \Third\, n.
1. The quotient of a unit divided by three; one of three
equal parts into which anything is divided.
2. The sixtieth part of a second of time.
3. (Mus.) The third tone of the scale; the mediant.
4. pl. (Law) The third part of the estate of a deceased
husband, which, by some local laws, the widow is entitled
to enjoy during her life.
Major third (Mus.), an interval of two tones.
Minor third (Mus.), an interval of a tone and a half.