The Collaborative International Dictionary of English v.0.48:

Regulate \Reg"u*late\ (-l[=a]t), v. t. [imp. & p. p. Regulated
   (-l[=a]`t[e^]d); p. pr. & vb. n. Regulating.] [L.
   regulatus, p. p. of regulare, fr. regula. See Regular.]
   1. To adjust by rule, method, or established mode; to direct
      by rule or restriction; to subject to governing principles
      or laws.
      [1913 Webster]

            The laws which regulate the successions of the
            seasons. --Macaulay.
      [1913 Webster]

            The herdsmen near the frontier adjudicated their own
            disputes, and regulated their own police.
                                                  --Bancroft.
      [1913 Webster]

   2. To put in good order; as, to regulate the disordered state
      of a nation or its finances.
      [1913 Webster]

   3. To adjust, or maintain, with respect to a desired rate,
      degree, or condition; as, to regulate the temperature of a
      room, the pressure of steam, the speed of a machine, etc.
      [1913 Webster]

   To regulate a watch or To regulate a clock, to adjust its
      rate of running so that it will keep approximately
      standard time.
      [1913 Webster]

   Syn: To adjust; dispose; methodize; arrange; direct; order;
        rule; govern.
        [1913 Webster]

WordNet (r) 3.0 (2006):

regulate
    v 1: fix or adjust the time, amount, degree, or rate of;
         "regulate the temperature"; "modulate the pitch" [syn:
         regulate, modulate]
    2: bring into conformity with rules or principles or usage;
       impose regulations; "We cannot regulate the way people
       dress"; "This town likes to regulate" [syn: regulate,
       regularize, regularise, order, govern] [ant:
       deregulate]
    3: shape or influence; give direction to; "experience often
       determines ability"; "mold public opinion" [syn: determine,
       shape, mold, influence, regulate]
    4: check the emission of (sound) [syn: baffle, regulate]

Moby Thesaurus II by Grady Ward, 1.0:

173 Moby Thesaurus words for "regulate":
   abate, accommodate, accord, adapt, adjust, adjust to, administer,
   administrate, alter, arrange, array, assimilate, assimilate to,
   assuage, attune, authorize, balance, be master, be responsible for,
   box in, call the shots, call the signals, captain, carry on, chair,
   chart, circumscribe, codify, command, condition, conduct,
   constitute, control, cool off, coordinate, cut to, damp, decide,
   declare lawful, decree, deploy, determine, diminish, direct,
   discipline, dispose, enact, engineer, equalize, equilibrize,
   establish, even, fit, fix, flatten, form, formulate, gear to,
   govern, grade, guide, handle, harmonize, head, head up, hedge,
   hedge about, hierarchize, homogenize, homologate, homologize,
   key to, lay out, lead, lead on, leaven, legalize, legislate,
   legitimate, legitimatize, legitimize, level, limit, line up,
   maintain, make a regulation, make legal, make plumb,
   make the rules, make uniform, manage, maneuver, manipulate,
   marshal, mastermind, measure, methodize, mitigate, moderate,
   modify, modulate, monitor, narrow, normalize, officer, operate,
   ordain, order, organize, oversee, pacify, palliate, plan,
   prescribe, preside over, proportion, pull the strings,
   put in force, put in tune, qualify, quarterback, quiet, rank,
   rationalize, reconcile, rectify, reduce, regularize, regulate by,
   restrain, restrict, right, routinize, rule, run, sanction, season,
   set, set conditions, set limits, set right, set up, settle,
   similarize, skipper, smooth, soften, stabilize, stand over,
   standardize, steer, stereotype, structure, superintend, supervise,
   symmetrize, sync, synchronize, systematize, tailor, take command,
   take the lead, temper, tranquilize, trim to, true, true up, tune,
   tune up, uniformize, validate, wear the pants, wield authority