The Collaborative International Dictionary of English v.0.48:

Subscribe \Sub*scribe"\, v. t. [imp. & p. p. Subscribed; p.
   pr. & vb. n. Subscribing.] [L. subscribere, subscriptum;
   sub under + scribere to write: cf. F. souscrire. See
   Scribe.]
   1. To write underneath, as one's name; to sign (one's name)
      to a document.
      [1913 Webster]

            [They] subscribed their names under them. --Sir T.
                                                  More.
      [1913 Webster]

   2. To sign with one's own hand; to give consent to, as
      something written, or to bind one's self to the terms of,
      by writing one's name beneath; as, parties subscribe a
      covenant or contract; a man subscribes a bond.
      [1913 Webster]

            All the bishops subscribed the sentence. --Milman.
      [1913 Webster]

   3. To attest by writing one's name beneath; as, officers
      subscribe their official acts, and secretaries and clerks
      subscribe copies or records.
      [1913 Webster]

   4. To promise to give, by writing one's name with the amount;
      as, each man subscribed ten dollars.
      [1913 Webster]

   5. To sign away; to yield; to surrender. [Obs.] --Shak.
      [1913 Webster]

   6. To declare over one's signature; to publish. [Obs.]
      [1913 Webster]

            Either or must shortly hear from him, or I will
            subscribe him a coward.               --Shak.
      [1913 Webster]

The Free On-line Dictionary of Computing (30 December 2018):

subscribe
subscribing

    To request to receive messages posted to a
   mailing list or newsgroup.  In contrast to the mundane use
   of the word this is often free of charge.

   (1997-03-27)