upsilon: Meaning and Definition of

up•si•lon

Pronunciation: (yp'su-lon", -lun, up'- esp. Brit. yp-sī'lun), [key]
— n.
  1. the 20th letter of the Greek alphabet (&Ugr;, &ugr;).
  2. the vowel sound represented by this letter.
  3. Also calledany of a family of heavy, short-lived, neutral mesons that are composed of a bottom quark and its antiquark. Symbol: &Ugr;, &ugr;
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.
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