Source : Webster's Revised Unabridged Dictionary (1913)

Columella \Col`u*mel"la\, n. [L., dim. of columen column. See
   {Column}.]
   1. (Bot.)
      (a) An axis to which a carpel of a compound pistil may be
          attached, as in the case of the geranium; or which is
          left when a pod opens.
      (b) A columnlike axis in the capsules of mosses.

   2. (Anat.) A term applied to various columnlike parts; as,
      the columella, or epipterygoid bone, in the skull of many
      lizards; the columella of the ear, the bony or
      cartilaginous rod connecting the tympanic membrane with
      the internal ear.

   3. (Zo["o]l.)
      (a) The upright pillar in the axis of most univalve
          shells.
      (b) The central pillar or axis of the calicles of certain
          corals.

Source : WordNet®

columella
     n : a small column (or structure resembling a column) that is a
         part of a plant or animal
     [also: {columellae} (pl)]