The Collaborative International Dictionary of English v.0.48:

Force \Force\, v. t. [imp. & p. p. Forced; p. pr. & vb. n.
   Forcing.] [OF. forcier, F. forcer, fr. LL. forciare,
   fortiare. See Force, n.]
   1. To constrain to do or to forbear, by the exertion of a
      power not resistible; to compel by physical, moral, or
      intellectual means; to coerce; as, masters force slaves to
      labor.
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   2. To compel, as by strength of evidence; as, to force
      conviction on the mind.
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   3. To do violence to; to overpower, or to compel by violence
      to one's will; especially, to ravish; to violate; to
      commit rape upon.
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            To force their monarch and insult the court.
                                                  --Dryden.
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            I should have forced thee soon wish other arms.
                                                  --Milton.
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            To force a spotless virgin's chastity. --Shak.
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   4. To obtain, overcome, or win by strength; to take by
      violence or struggle; specifically, to capture by assault;
      to storm, as a fortress; as, to force the castle; to force
      a lock.
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   5. To impel, drive, wrest, extort, get, etc., by main
      strength or violence; -- with a following adverb, as
      along, away, from, into, through, out, etc.
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            It stuck so fast, so deeply buried lay
            That scarce the victor forced the steel away.
                                                  --Dryden.
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            To force the tyrant from his seat by war. --Sahk.
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            Ethelbert ordered that none should be forced into
            religion.                             --Fuller.
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   6. To put in force; to cause to be executed; to make binding;
      to enforce. [Obs.]
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            What can the church force more?       --J. Webster.
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   7. To exert to the utmost; to urge; hence, to strain; to urge
      to excessive, unnatural, or untimely action; to produce by
      unnatural effort; as, to force a conceit or metaphor; to
      force a laugh; to force fruits.
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            High on a mounting wave my head I bore,
            Forcing my strength, and gathering to the shore.
                                                  --Dryden.
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   8. (Whist) To compel (an adversary or partner) to trump a
      trick by leading a suit of which he has none.
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   9. To provide with forces; to re["e]nforce; to strengthen by
      soldiers; to man; to garrison. [Obs.] --Shak.
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   10. To allow the force of; to value; to care for. [Obs.]
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             For me, I force not argument a straw. --Shak.

   Syn: To compel; constrain; oblige; necessitate; coerce;
        drive; press; impel.
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The Collaborative International Dictionary of English v.0.48:

Forced \Forced\, a.
   Done or produced with force or great labor, or by
   extraordinary exertion; hurried; strained; produced by
   unnatural effort or pressure; as, a forced style; a forced
   laugh.
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   Forced draught. See under Draught.

   Forced march (Mil.), a march of one or more days made with
      all possible speed. -- For"ced*ly, adv. --
      For"ced*ness, n.
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WordNet (r) 3.0 (2006):

forced
    adj 1: produced by or subjected to forcing; "forced-air
           heating"; "furnaces of the forced-convection type";
           "forced convection in plasma generators"
    2: forced or compelled; "promised to abolish forced labor"
    3: made necessary by an unexpected situation or emergency; "a
       forced landing"
    4: lacking spontaneity; not natural; "a constrained smile";
       "forced heartiness"; "a strained smile" [syn: constrained,
       forced, strained]

Moby Thesaurus II by Grady Ward, 1.0:

107 Moby Thesaurus words for "forced":
   Herculean, Latinate, affected, arduous, artificial, at odds,
   automatic, averse, awkward, backbreaking, blind, bombastic,
   burdensome, calculated, coerced, compelled, compulsive,
   conditioned, constrained, contrived, cramped, crushing, cumbrous,
   cursory, differing, disagreeing, disinclined, disobedient, distant,
   effortful, elephantine, exhausting, factitious, faked, false,
   farfetched, fatiguing, feigned, formal, fractious, grueling,
   guinde, halting, hard-earned, hard-fought, heavy, hefty,
   improbable, impulsive, indisposed, indocile, inflexible, inkhorn,
   instinctive, involuntary, killing, labored, laborious, leaden,
   lumbering, mannered, mechanical, mutinous, onerous, operose,
   opposed, oppressive, out-of-the-way, painful, perfunctory, pompous,
   ponderous, punishing, quite another thing, recalcitrant, reflex,
   reflexive, refractory, remote, resistant, rigid, self-conscious,
   sesquipedalian, something else again, stiff, stilted, strained,
   strenuous, studied, sulky, sullen, toilsome, tough, troublesome,
   turgid, unconscious, unconsenting, unintentional, unnatural,
   unthinking, unwieldy, unwilled, unwilling, unwitting, uphill,
   wearisome, wooden