The Collaborative International Dictionary of English v.0.48:

Punctuate \Punc"tu*ate\, v. t. [imp. & p. p. Punctuated; p.
   pr. & vb. n. Punctuating.] [Cf. F. ponctuer. See
   Punctual.]
   To mark with points; to separate into sentences, clauses,
   etc., by points or stops which mark the proper pauses in
   expressing the meaning.
   [1913 Webster]

WordNet (r) 3.0 (2006):

punctuate
    v 1: insert punctuation marks into [syn: punctuate, mark]
    2: to stress, single out as important; "Dr. Jones emphasizes
       exercise in addition to a change in diet" [syn: stress,
       emphasize, emphasise, punctuate, accent,
       accentuate]
    3: interrupt periodically; "Her sharp questions punctuated the
       speaker's drone"