The Collaborative International Dictionary of English v.0.48:

Relax \Re*lax"\, v. i.
   1. To become lax, weak, or loose; as, to let one's grasp
      relax.
      [1913 Webster]

            His knees relax with toil.            --Pope.
      [1913 Webster]

   2. To abate in severity; to become less rigorous.
      [1913 Webster]

            In others she relaxed again,
            And governed with a looser rein.      --Prior.
      [1913 Webster]

   3. To remit attention or effort; to become less diligent; to
      unbend; as, to relax in study.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Relax \Re*lax"\ (r?-l?ks"), v. t. [imp. & p. p. Relaxed
   (-l?kst"); p. pr. & vb. n. Relaxing.] [L. relaxare; pref.
   re- re- + laxare to loose, to slacken, from laxus loose. See
   Lax, and cf. Relay, n., Release.]
   1. To make lax or loose; to make less close, firm, rigid,
      tense, or the like; to slacken; to loosen; to open; as, to
      relax a rope or cord; to relax the muscles or sinews.
      [1913 Webster]

            Horror . . . all his joints relaxed.  --Milton.
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            Nor served it to relax their serried files.
                                                  --Milton.
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   2. To make less severe or rigorous; to abate the stringency
      of; to remit in respect to strenuousness, earnestness, or
      effort; as, to relax discipline; to relax one's attention
      or endeavors.
      [1913 Webster]

            The statute of mortmain was at several times relaxed
            by the legislature.                   --Swift.
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   3. Hence, to relieve from attention or effort; to ease; to
      recreate; to divert; as, amusement relaxes the mind.
      [1913 Webster]

   4. To relieve from constipation; to loosen; to open; as, an
      aperient relaxes the bowels.
      [1913 Webster]

   Syn: To slacken; loosen; loose; remit; abate; mitigate; ease;
        unbend; divert.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Relax \Re*lax"\, n.
   Relaxation. [Obs.] --Feltham.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Relax \Re**lax"\, a.
   Relaxed; lax; hence, remiss; careless.
   [1913 Webster]

WordNet (r) 3.0 (2006):

relax
    v 1: become less tense, rest, or take one's ease; "He relaxed in
         the hot tub"; "Let's all relax after a hard day's work"
         [syn: relax, loosen up, unbend, unwind,
         decompress, slow down] [ant: tense, tense up]
    2: make less taut; "relax the tension on the rope" [syn:
       relax, unbend]
    3: become loose or looser or less tight; "The noose loosened";
       "the rope relaxed" [syn: loosen, relax, loose] [ant:
       stiffen]
    4: cause to feel relaxed; "A hot bath always relaxes me" [syn:
       relax, unstrain, unlax, loosen up, unwind, make
       relaxed] [ant: strain, tense, tense up]
    5: become less tense, less formal, or less restrained, and
       assume a friendlier manner; "our new colleague relaxed when
       he saw that we were a friendly group" [syn: relax, loosen
       up]
    6: make less severe or strict; "The government relaxed the
       curfew after most of the rebels were caught" [syn: relax,
       loosen]
    7: become less severe or strict; "The rules relaxed after the
       new director arrived" [syn: relax, loosen]
    8: make less active or fast; "He slackened his pace as he got
       tired"; "Don't relax your efforts now" [syn: slack,
       slacken, slack up, relax]

Moby Thesaurus II by Grady Ward, 1.0:

185 Moby Thesaurus words for "relax":
   abate, admit, admit exceptions, allow, allow for, amuse, arrest,
   backpedal, backwater, bate, be at ease, be easy, be relaxed,
   beguile, beguile the time, bend, brake, calm down, check,
   clip the wings, collect, collect oneself, compose, compose oneself,
   concede, consider, consider the circumstances, consider the source,
   convulse, cool it, cool off, curb, cushion, decelerate, decrease,
   delay, delight, detain, diffuse, diminish, discount, disjoin,
   disperse, disregard, divert, draw rein, drown care, ease, ease off,
   ease up, enliven, entertain, exhilarate, feel at home, feel easy,
   fluff, forbear, forgive, fracture one, free, gentle, get organized,
   give, give quarter, give way, grant, have a ball, have fun,
   have mercy upon, have pity, hold back, hold in check, hold up,
   impede, keep back, kill, kill time, knead, knock dead, laugh it up,
   lax, laxate, lessen, let down, let go, let up, let up on,
   lift temporarily, limber, limber up, live it up, loose, loosen,
   loosen up, lose ground, lose momentum, lose speed, make,
   make allowance for, mash, massage, mellow, melt, milden, mitigate,
   moderate, modify, modulate, mollify, obstruct, pardon, plump,
   provide for, pulp, quiet down, raise a laugh, raise a smile,
   recreate, reduce, reef, refresh, regale, rein in,
   relax the condition, release, relent, relieve, remit, reprieve,
   rest, retard, scatter, set aside, set back, shake up, simmer down,
   slack, slack off, slack up, slacken, slake, slay, slow, slow down,
   slow up, smash, sober down, soften, soften up, solace, spare,
   squash, stand easy, stay, subdue, submit, supple, take account of,
   take in sail, take into account, take into consideration,
   take it easy, take pity on, temper, tenderize, thaw, throttle down,
   tickle, titillate, tone down, tune down, unbend, unbrace, unglue,
   unlax, unleash, unstick, unstrain, unstring, untighten, unwind,
   waive, weaken, wow, yield