Pronunciation: (yes'tur), [key]
of or pertaining to yesterday. Also,yestern.
a combining form, now unproductive, occurring in words that denote an extent of time one period prior to the present period, the nature of the period being specified by the second element of the compound: yesterweek.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.