Source : Webster's Revised Unabridged Dictionary (1913)

Yesterday \Yes"ter*day\, n. [OE. [yogh]isterdai, AS. geostran
   d[ae]g, from geostran, geostra, giestran, gistran, gystran,
   yesterday (akin to D. gisteren, G. gestern, OHG. gestaron,
   Icel. g[ae]r yesterday, to-morrow, Goth. gistradagis
   to-morrow, L. heri yesterday, Gr. ?, Skr. hyas) + d[ae]g day.
   Cf. {Hestern}. ????.]
   1. The day last past; the day next before the present.

            All our yesterdays have lighted fools The way to
            dusty death.                          --Shak.

            We are but of yesterday, and know nothing. --Job
                                                  viii. 9.

   2. Fig.: A recent time; time not long past.

            The proudest royal houses are but of yesterday, when
            compared with the line of supreme pontiffs.
                                                  --Macaulay.

Yesterday \Yes"ter*day\, adv.
   On the day last past; on the day preceding to-day; as, the
   affair took place yesterday.

Source : WordNet®

yesterday
     n 1: the day immediately before today; "it was in yesterday's
          newspapers"
     2: the recent past; "yesterday's solutions are not good
        enough"; "we shared many yesterdays"
     adv 1: on the day preceding today; "yesterday the weather was
            beautiful"
     2: in the recent past; only a short time ago; "I was not born
        yesterday!"