The Collaborative International Dictionary of English v.0.48:

Undated \Un*dat"ed\ ([u^]n*d[=a]t"[e^]d), a. [Pref. un- not +
   dated.]
   Not dated; having no date; of unknown age; as, an undated
   letter.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Undated \Un"da*ted\ ([u^]n"d[asl]*t[e^]d), a. [L. undatus, p. p.
   of undare to rise in waves, to wave, to undulate, fr. unda a
   wave. See Undulate.] (Bot.)
   Rising and falling in waves toward the margin, as a leaf;
   waved.
   [1913 Webster]

WordNet (r) 3.0 (2006):

undated
    adj 1: not bearing a date; "a dateless letter" [syn: dateless,
           undated]