Upsilon
Pronunciation : Up"si*lon, n. [Gr. 'y^ psilo`n bare, mere
Part of Speech : simple
Definition : Defn: The 20th letter (U, u) of the Greek alphabet, a vowel having originally the sound of oo as in room, becoming before the 4th century b. c. that French u or Ger. ?. Its equivalent in English is u or y.
y.]
Source : Webster's Unabridged Dictionary, 1913