next after the second; coming after two others; -- the ordinal of three; as, the third hour in the day.-constituting or being one of three equal parts into which anything is divided; as, the third part of a day.-the quotient of a unit divided by three; one of three equal parts into which anything is divided.-the sixtieth part of a second of time.-the third tone of the scale; the mediant.-the third part of the estate of a deceased husband, which, by some local laws, the widow is entitled to enjoy during her life.