The Collaborative International Dictionary of English v.0.48:

Enroll \En*roll"\, v. t. [imp. & p. p. Enrolled; p. pr. & vb.
   n. Enrolling.] [Pref. en- + roll: cf. F. enr[^o]ler; pref.
   en- (L. in) + r[^o]le roll or register. See Roll, n.]
   [Written also enrol.]
   1. To insert in a roil; to register or enter in a list or
      catalogue or on rolls of court; hence, to record; to
      insert in records; to leave in writing; as, to enroll men
      for service; to enroll a decree or a law; also,
      reflexively, to enlist.
      [1913 Webster]

            An unwritten law of common right, so engraven in the
            hearts of our ancestors, and by them so constantly
            enjoyed and claimed, as that it needed not
            enrolling.                            --Milton.
      [1913 Webster]

            All the citizen capable of bearing arms enrolled
            themselves.                           --Prescott.
      [1913 Webster]

   2. To envelop; to inwrap; to involve. [Obs.] --Spenser.
      [1913 Webster]

WordNet (r) 3.0 (2006):

enroll
    v 1: register formally as a participant or member; "The party
         recruited many new members" [syn: enroll, inscribe,
         enter, enrol, recruit]

Moby Thesaurus II by Grady Ward, 1.0:

106 Moby Thesaurus words for "enroll":
   affiliate, affiliate with, associate, book, calendar, call up,
   carve, catalog, chalk, chalk up, check in, chronicle, combine,
   come into, commandeer, conscript, creep in, cut, detach,
   detach for service, docket, draft, engrave, enlist, enscroll,
   enter, enumerate, file, fill out, get into, go into, grave,
   impanel, impress, inaugurate, incise, index, induct, initiate,
   inscribe, insert, install, instate, inventory, invest, itemize,
   join, join up, jot down, keep score, league with, levy, line up,
   list, log, make a memorandum, make a note, make an entry, make out,
   mark down, matriculate, minute, mobilize, muster, muster in, note,
   note down, ordain, pigeonhole, place upon record, poll, post,
   post up, press, program, put down, put in writing, put on paper,
   put on tape, raise, record, recruit, reduce to writing, register,
   schedule, score, set down, sign on, sign up, sneak in, summon,
   tabulate, take down, take out membership, take up membership,
   tally, tape, tape-record, team up with, team with, videotape,
   write, write down, write in, write out, write up