The Collaborative International Dictionary of English v.0.48:

Punctum \Punc"tum\, n. [L., a point.]
   A point.
   [1913 Webster]

   Punctum c[ae]cum. [L., blind point.] (Anat.) Same as Blind
      spot, under Blind.

   Punctum proximum, near point. See under Point.

   Punctum remotum, far point. See under Point.

   Punctum vegetationis [L., point of vegetation] (Bot.), the
      terminal cell of a stem, or of a leaf bud, from which new
      growth originates.
      [1913 Webster]

WordNet (r) 3.0 (2006):

punctum
    n 1: (anatomy) a point or small area