The Collaborative International Dictionary of English v.0.48:

Sign \Sign\, v. t. [imp. & p. p. Signed; p. pr. & vb. n.
   Signing.] [OE. seinen to bless, originally, to make the
   sign of the cross over; in this sense fr. ASS. segnian (from
   segn, n.), or OF. seignier, F. signer, to mark, to sign (in
   sense 3), fr. L. signare to mark, set a mark upon, from
   signum. See Sign, n.]
   1. To represent by a sign; to make known in a typical or
      emblematic manner, in distinction from speech; to signify.
      [1913 Webster]

            I signed to Browne to make his retreat. --Sir W.
                                                  Scott.
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   2. To make a sign upon; to mark with a sign.
      [1913 Webster]

            We receive this child into the congregation of
            Christ's flock, and do sign him with the sign of the
            cross.                                --Bk. of Com
                                                  Prayer.
      [1913 Webster]

   3. To affix a signature to; to ratify by hand or seal; to
      subscribe in one's own handwriting.
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            Inquire the Jew's house out, give him this deed,
            And let him sign it.                  --Shak.
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   4. To assign or convey formally; -- used with away.
      [1913 Webster]

   5. To mark; to make distinguishable. --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

signed
    adj 1: having a handwritten signature; "a signed letter" [ant:
           unsigned]
    2: used of the language of the deaf [syn: gestural, sign(a),
       signed, sign-language(a)]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "signed":
   accepted, acknowledged, admitted, affirmed, agreed, allowed,
   approved, arranged, authenticated, avowed, certified, compacted,
   conceded, confessed, confirmed, contracted, countersigned,
   covenanted, endorsed, engaged, granted, notarized, professed,
   promised, ratified, received, recognized, sealed, settled, stamped,
   stipulated, sworn and affirmed, sworn to, undertaken, underwritten,
   validated, warranted