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.
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            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.
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            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.
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   4. To relieve from constipation; to loosen; to open; as, an
      aperient relaxes the bowels.
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   Syn: To slacken; loosen; loose; remit; abate; mitigate; ease;
        unbend; divert.
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WordNet (r) 3.0 (2006):

relaxed
    adj 1: without strain or anxiety; "gave the impression of being
           quite relaxed"; "a relaxed and informal discussion" [ant:
           tense]