Definition of y :
1. A forked or bifurcated pipe fitting.
2. A portion of track consisting of two diverging tracks connected by a cross track.
4. One of the forked holders for supporting the telescope of a leveling instrument, or the axis of a theodolite; a wye.
5. Something shaped like the letter Y; a forked piece resembling in form the letter Y.
6. Y, the twenty- fifth letter of the English alphabet, at the beginning of a word or syllable, except when a prefix ( see Y-), is usually a fricative vocal consonant; as a prefix, and usually in the middle or at the end of a syllable, it is a vowel.