The Collaborative International Dictionary of English v.0.48:

Think \Think\, v. t. [imp. & p. p. Thought; p. pr. & vb. n.
   Thinking.] [OE. thinken, properly, to seem, from AS.
   [thorn]yncean (cf. Methinks), but confounded with OE.
   thenken to think, fr. AS. [thorn]encean (imp.
   [thorn][=o]hte); akin to D. denken, dunken, OS. thenkian,
   thunkian, G. denken, d["u]nken, Icel. [thorn]ekkja to
   perceive, to know, [thorn]ykkja to seem, Goth. [thorn]agkjan,
   [thorn]aggkjan, to think, [thorn]ygkjan to think, to seem,
   OL. tongere to know. Cf. Thank, Thought.]
   1. To seem or appear; -- used chiefly in the expressions
      methinketh or methinks, and methought.
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   Note: These are genuine Anglo-Saxon expressions, equivalent
         to it seems to me, it seemed to me. In these
         expressions me is in the dative case.
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   2. To employ any of the intellectual powers except that of
      simple perception through the senses; to exercise the
      higher intellectual faculties.
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            For that I am
            I know, because I think.              --Dryden.
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   3. Specifically:
      (a) To call anything to mind; to remember; as, I would
          have sent the books, but I did not think of it.
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                Well thought upon; I have it here. --Shak.
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      (b) To reflect upon any subject; to muse; to meditate; to
          ponder; to consider; to deliberate.
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                And when he thought thereon, he wept. --Mark
                                                  xiv. 72.
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                He thought within himself, saying, What shall I
                do, because I have no room where to bestow my
                fruits?                           --Luke xii.
                                                  17.
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      (c) To form an opinion by reasoning; to judge; to
          conclude; to believe; as, I think it will rain
          to-morrow.
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                Let them marry to whom they think best. --Num.
                                                  xxxvi. 6.
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      (d) To purpose; to intend; to design; to mean.
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                I thought to promote thee unto great honor.
                                                  --Num. xxiv.
                                                  11.
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                Thou thought'st to help me.       --Shak.
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      (e) To presume; to venture.
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                Think not to say within yourselves, We have
                Abraham to our father.            --Matt. iii.
                                                  9.
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   Note: To think, in a philosophical use as yet somewhat
         limited, designates the higher intellectual acts, the
         acts preeminently rational; to judge; to compare; to
         reason. Thinking is employed by Hamilton as
         "comprehending all our collective energies." It is
         defined by Mansel as "the act of knowing or judging by
         means of concepts,"by Lotze as "the reaction of the
         mind on the material supplied by external influences."
         See Thought.
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   To think better of. See under Better.

   To think much of, or To think well of, to hold in esteem;
      to esteem highly.
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   Syn: To expect; guess; cogitate; reflect; ponder;
        contemplate; meditate; muse; imagine; suppose; believe.
        See Expect, Guess.
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The Collaborative International Dictionary of English v.0.48:

Think \Think\, n.
   Act of thinking; a thought. "If you think that I'm finished,
   you've got another think coming!" [Obs. or Colloq.]
   [Webster 1913 Suppl. +PJC]

The Collaborative International Dictionary of English v.0.48:

Think \Think\, v. t.
   1. To conceive; to imagine.
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            Charity . . . thinketh no evil.       --1 Cor. xiii.
                                                  4,5.
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   2. To plan or design; to plot; to compass. [Obs.]
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            So little womanhood
            And natural goodness, as to think the death
            Of her own son.                       --Beau. & Fl.
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   3. To believe; to consider; to esteem.
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            Nor think superfluous other's aid.    --Milton.
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   To think much, to esteem a great matter; to grudge. [Obs.]
      "[He] thought not much to clothe his enemies." --Milton.

   To think scorn.
      (a) To disdain. [Obs.] "He thought scorn to lay hands on
          Mordecai alone." --Esther iii. 6.
      (b) To feel indignation. [Obs.]
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WordNet (r) 3.0 (2006):

think
    n 1: an instance of deliberate thinking; "I need to give it a
         good think"
    v 1: judge or regard; look upon; judge; "I think he is very
         smart"; "I believe her to be very smart"; "I think that he
         is her boyfriend"; "The racist conceives such people to be
         inferior" [syn: think, believe, consider, conceive]
    2: expect, believe, or suppose; "I imagine she earned a lot of
       money with her new novel"; "I thought to find her in a bad
       state"; "he didn't think to find her in the kitchen"; "I
       guess she is angry at me for standing her up" [syn: think,
       opine, suppose, imagine, reckon, guess]
    3: use or exercise the mind or one's power of reason in order to
       make inferences, decisions, or arrive at a solution or
       judgments; "I've been thinking all day and getting nowhere"
       [syn: think, cogitate, cerebrate]
    4: recall knowledge from memory; have a recollection; "I can't
       remember saying any such thing"; "I can't think what her last
       name was"; "can you remember her phone number?"; "Do you
       remember that he once loved you?"; "call up memories" [syn:
       remember, retrieve, recall, call back, call up,
       recollect, think] [ant: blank out, block, draw a
       blank, forget]
    5: imagine or visualize; "Just think--you could be rich one
       day!"; "Think what a scene it must have been!"
    6: focus one's attention on a certain state; "Think big"; "think
       thin"
    7: have in mind as a purpose; "I mean no harm"; "I only meant to
       help you"; "She didn't think to harm me"; "We thought to
       return early that night" [syn: intend, mean, think]
    8: decide by pondering, reasoning, or reflecting; "Can you think
       what to do next?"
    9: ponder; reflect on, or reason about; "Think the matter
       through"; "Think how hard life in Russia must be these days"
    10: dispose the mind in a certain way; "Do you really think so?"
    11: have or formulate in the mind; "think good thoughts"
    12: be capable of conscious thought; "Man is the only creature
        that thinks"
    13: bring into a given condition by mental preoccupation; "She
        thought herself into a state of panic over the final exam"

Moby Thesaurus II by Grady Ward, 1.0:

165 Moby Thesaurus words for "think":
   account as, aim, aim at, anticipate, appreciate, aspire after,
   aspire to, assess, assume, be afraid, be after, be concerned,
   believe, brood, call to mind, care, cerebrate, cogitable, cogitate,
   come up with, comprehend, comprehensible, conceivable, conceive,
   conceptualize, conclude, concoct, conjecture, consider,
   contemplate, contrive, convincing, create, credit, daresay, deduce,
   deem, deliberate, design, desire, destine, determine, devise,
   divine, dread, dream, dream up, drive at, entertain ideas,
   envisage, envision, esteem, estimate, evaluate, exercise the mind,
   expect, face, fancy, fantasize, feasible, feature, feel, foresee,
   form ideas, gather, go for, grant, guess, harbor a design,
   have a hunch, have an idea, have an impression, have an inkling,
   have every intention, have in mind, have the idea, heed, hold,
   hold as, hope, ideate, image, imaginable, imagine, improvise,
   infer, intellectualize, intend, invent, judge, let, let be, likely,
   logicalize, logicize, look upon as, maintain, make up, mark, mean,
   meditate, mind, mull, mull over, muse, muse over, opine,
   pay attention, plan, plausible, ponder, possible, practicable,
   practical, prefigure, presumable, presume, presuppose, presurmise,
   pretend, project, propose, provisionally accept, purport, purpose,
   rationalize, realize, reason, recall, reck, reckon, recollect,
   reflect, regard, remember, repute, resolve, ruminate,
   ruminate over, say, see, sense, set down as, speculate, study,
   supposable, suppose, surmise, suspect, take, take an interest,
   take for, take for granted, take it, take to be, think of,
   thinkable, trow, understand, value, view as, vision, visualize,
   ween, weigh