The Collaborative International Dictionary of English v.0.48:

Lapse \Lapse\, v. i. [imp. & p. p. Lapsed; p. pr. & vb. n.
   Lapsing.]
   1. To pass slowly and smoothly downward, backward, or away;
      to slip downward, backward, or away; to glide; -- mostly
      restricted to figurative uses.
      [1913 Webster]

            A tendency to lapse into the barbarity of those
            northern nations from whom we are descended.
                                                  --Swift.
      [1913 Webster]

            Homer, in his characters of Vulcan and Thersites,
            has lapsed into the burlesque character. --Addison.
      [1913 Webster]

   2. To slide or slip in moral conduct; to fail in duty; to
      fall from virtue; to deviate from rectitude; to commit a
      fault by inadvertence or mistake.
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            To lapse in fullness
            Is sorer than to lie for need.        --Shak.
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   3. (Law)
      (a) To fall or pass from one proprietor to another, or
          from the original destination, by the omission,
          negligence, or failure of some one, as a patron, a
          legatee, etc.
      (b) To become ineffectual or void; to fall.
          [1913 Webster]

                If the archbishop shall not fill it up within
                six months ensuing, it lapses to the king.
                                                  --Ayliffe.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lapsed \Lapsed\, a.
   1. Having slipped downward, backward, or away; having lost
      position, privilege, etc., by neglect; -- restricted to
      figurative uses.
      [1913 Webster]

            Once more I will renew
            His lapsed powers, though forfeit.    --Milton.
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   2. Ineffectual, void, or forfeited; as, a lapsed policy of
      insurance; a lapsed legacy.
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   Lapsed devise, Lapsed legacy (Law), a devise, or legacy,
      which fails to take effect in consequence of the death of
      the devisee, or legatee, before that of the testator, or
      for other cause. --Wharton (Law Dict.).
      [1913 Webster]

WordNet (r) 3.0 (2006):

lapsed
    adj 1: no longer active or practicing; "a lapsed Catholic" [syn:
           lapsed, nonchurchgoing]

Moby Thesaurus II by Grady Ward, 1.0:

94 Moby Thesaurus words for "lapsed":
   Adamic, Circean, ago, animal, animalistic, antiquated, antique,
   apostate, atheistic, backsliding, beastlike, beastly, bestial,
   blasphemous, blown over, bodily, brutal, brute, brutish, by,
   bygone, bypast, carnal, carnal-minded, coarse, dated, dead,
   dead and buried, deceased, defunct, departed, earthy, elapsed,
   erring, expired, extinct, fallen, fallen from grace, finished,
   fleshly, forgotten, frail, gone, gone glimmering, gone-by, gross,
   has-been, impious, impure, infirm, irrecoverable, irreligious,
   irreverent, material, materialistic, no more, nonspiritual,
   obsolete, of easy virtue, orgiastic, over, passe, passed,
   passed away, past, peccable, physical, postlapsarian, prodigal,
   profanatory, profane, recidivist, recidivistic, recreant, renegade,
   run out, sacrilegious, swinish, unangelic, unchaste, unclean,
   undutiful, ungodly, ungood, unrighteous, unsaintly, unspiritual,
   unvirtuous, vanished, virtueless, wanton, wayward, weak,
   wound up