1. [n]  (informal) an instance of deliberate thinking; "I need to give it a good think"
2. [v]  bring into a given condition by mental preoccupation; "She thought herself into a state of panic over the final exam"
3. [v]  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"
4. [v]  be capable of conscious thought; "Man is the only creature that thinks"
5. [v]  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"
6. [v]  have or formulate in the mind; "think good thoughts"
7. [v]  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"
8. [v]  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"
9. [v]  dispose the mind in a certain way; "Do you really think so?"
10. [v]  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"
11. [v]  focus one's attention on a certain state; "Think big"; "think thin"
12. [v]  ponder; reflect on, or reason about; "Think the matter through"; "Think how hard life in Russia must be these days"
13. [v]  decide by pondering, reasoning, or reflecting; "Can you think what to do next?"
14. [v]  imagine or visualize; "Just think--you could be rich one day!"; "Think what a scene it must have been!"

Think
Blackburn, author of the OXFORD DICTIONARY OF PHILOSOPHY, provides the curious with an accessible and intelligent introduction to the major issues of philosophy and how they have been addressed.

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1. \Think\, n.
   Act of thinking; a thought. [Obs. or Colloq.]
   

2. \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.
   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.
   2. To employ any of the intellectual powers except that of
      simple perception through the senses; to exercise the
      higher intellectual faculties.
            For that I am I know, because I think. --Dryden.
   3. Specifically:
      (a) To call anything to mind; to remember; as, I would
          have sent the books, but I did not think of it.
                Well thought upon; I have it here. --Shak.
      (b) To reflect upon any subject; to muse; to meditate; to
          ponder; to consider; to deliberate.
                And when he thought thereon, he wept. --Mark
                                                  xiv. 72.
                He thought within himself, saying, What shall I
                do, because I have no room where to bestow my
                fruits?                           --Luke xii.
                                                  17.
      (c) To form an opinion by reasoning; to judge; to
          conclude; to believe; as, I think it will rain
          to-morrow.
                Let them marry to whom they think best. --Num.
                                                  xxxvi. 6.
      (d) To purpose; to intend; to design; to mean.
                I thought to promote thee unto great honor.
                                                  --Num. xxiv.
                                                  11.
                Thou thought'st to help me.       --Shak.
      (e) To presume; to venture.
                Think not to say within yourselves, We have
                Abraham to our father.            --Matt. iii.
                                                  9.
   Note: To think, in a philosophical use as yet somewhat
         limited, designates the higher intellectual acts, the
         acts pre["e]minently 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}.
   {To think better of}. See under {Better}.
   {To think much of}, or {To think well of}, to hold in esteem;
      to esteem highly.
   Syn: To expect; guess; cogitate; reflect; ponder;
        contemplate; meditate; muse; imagine; suppose; believe.
        See {Expect}, {Guess}.
   

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