The Collaborative International Dictionary of English v.0.48:

Teach \Teach\ (t[=e]ch), v. t. [imp. & p. p. Taught (t[add]t);
   p. pr. & vb. n. Teaching.] [OE. techen, imp. taughte,
   tahte, AS. t[=ae]cean, imp. t[=ae]hte, to show, teach, akin
   to t[=a]cn token. See Token.]
   1. To impart the knowledge of; to give intelligence
      concerning; to impart, as knowledge before unknown, or
      rules for practice; to inculcate as true or important; to
      exhibit impressively; as, to teach arithmetic, dancing,
      music, or the like; to teach morals.
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            If some men teach wicked things, it must be that
            others should practice them.          --South.
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   2. To direct, as an instructor; to manage, as a preceptor; to
      guide the studies of; to instruct; to inform; to conduct
      through a course of studies; as, to teach a child or a
      class. "He taught his disciples." --Mark ix. 31.
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            The village master taught his little school.
                                                  --Goldsmith.
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   3. To accustom; to guide; to show; to admonish.
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            I shall myself to herbs teach you.    --Chaucer.
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            They have taught their tongue to speak lies. --Jer.
                                                  ix. 5.
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   Note: This verb is often used with two objects, one of the
         person, the other of the thing; as, he taught me Latin
         grammar. In the passive construction, either of these
         objects may be retained in the objective case, while
         the other becomes the subject; as, I was taught Latin
         grammar by him; Latin grammar was taught me by him.
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   Syn: To instruct; inform; inculcate; tell; guide; counsel;
        admonish. See the Note under Learn.
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The Collaborative International Dictionary of English v.0.48:

Teach \Teach\, v. i.
   To give instruction; to follow the business, or to perform
   the duties, of a preceptor.
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         And gladly would he learn, and gladly teach. --Chaucer.
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         The priests thereof teach for hire.      --Micah iii.
                                                  11.
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WordNet (r) 3.0 (2006):

Teach
    n 1: an English pirate who operated in the Caribbean and off the
         Atlantic coast of North America (died in 1718) [syn:
         Teach, Edward Teach, Thatch, Edward Thatch,
         Blackbeard]
    v 1: impart skills or knowledge to; "I taught them French"; "He
         instructed me in building a boat" [syn: teach, learn,
         instruct]
    2: accustom gradually to some action or attitude; "The child is
       taught to obey her parents"

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "teach":
   broaden the mind, catechize, civilize, coach, communicate,
   demonstrate, direct, discipline, drill, edify, educate, enlighten,
   exercise, give instruction, give lessons in, ground, guide,
   illumine, impart, implant, inculcate, indoctrinate, inform,
   instill, instruct, instruction, lesson, open the eyes, practice,
   prepare, rear, reeducate, school, schooling, set right,
   sharpen the wits, show, show how, teach a lesson,
   teach the rudiments, teaching, train, training, tuition, tutelage,
   tutor