Pronunciation: (tou, tô for 1, 2, 4; täv, tôv for 3), [key]
1. the 19th letter of the Greek alphabet (T, τ).
2. the consonant sound represented by this letter.
4. Also,tauon. Physics.See tau lepton.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.