Source : Webster's Revised Unabridged Dictionary (1913)

Acinus \Ac"i*nus\, n.; pl. {Acini}. [L., grape, grapestone.]
   1. (Bot.)
      (a) One of the small grains or drupelets which make up
          some kinds of fruit, as the blackberry, raspberry,
          etc.
      (b) A grapestone.

   2. (Anat.) One of the granular masses which constitute a
      racemose or compound gland, as the pancreas; also, one of
      the saccular recesses in the lobules of a racemose gland.
      --Quain.

Source : WordNet®

acinus
     n 1: one of the small drupes making up an aggregate or multiple
          fruit like a blackberry
     2: one of the small sacs or saclike dilations in a compound
        gland
     [also: {acini} (pl)]