Source : Webster's Revised Unabridged Dictionary (1913)

Thou \Thou\, v. t.
   To address as thou, esp. to do so in order to treat with
   insolent familiarity or contempt.

         If thou thouest him some thrice, it shall not be amiss.
                                                  --Shak.

Thou \Thou\, pron. [Sing.: nom. {Thou}; poss. {Thy}or {Thine};
   obj. {Thee}. Pl.: nom. {You}; poss. {Your}or {Yours}; obj.
   {You}.] [OE. thou, [thorn]u, AS. [eth][=u], [eth]u; akin to
   OS. & OFries. thu, G., Dan. & Sw. du, Icel. [thorn][=u],
   Goth. [thorn]u, Russ. tui, Ir. & Gael. tu, W. ti, L. tu, Gr.
   sy`, Dor. ty`, Skr. tvam. [root]185. Cf. {Thee}, {Thine}, {Te
   Deum}.]
   The second personal pronoun, in the singular number, denoting
   the person addressed; thyself; the pronoun which is used in
   addressing persons in the solemn or poetical style.

         Art thou he that should come?            --Matt. xi. 3.

   Note: ``In Old English, generally, thou is the language of a
         lord to a servant, of an equal to an equal, and
         expresses also companionship, love, permission,
         defiance, scorn, threatening: whilst ye is the language
         of a servant to a lord, and of compliment, and further
         expresses honor, submission, or entreaty.'' --Skeat.

   Note: Thou is now sometimes used by the Friends, or Quakers,
         in familiar discourse, though most of them corruptly
         say thee instead of thou.

Thou \Thou\, pron. [Sing.: nom. {Thou}; poss. {Thy}or {Thine};
   obj. {Thee}. Pl.: nom. {You}; poss. {Your}or {Yours}; obj.
   {You}.] [OE. thou, [thorn]u, AS. [eth][=u], [eth]u; akin to
   OS. & OFries. thu, G., Dan. & Sw. du, Icel. [thorn][=u],
   Goth. [thorn]u, Russ. tui, Ir. & Gael. tu, W. ti, L. tu, Gr.
   sy`, Dor. ty`, Skr. tvam. [root]185. Cf. {Thee}, {Thine}, {Te
   Deum}.]
   The second personal pronoun, in the singular number, denoting
   the person addressed; thyself; the pronoun which is used in
   addressing persons in the solemn or poetical style.

         Art thou he that should come?            --Matt. xi. 3.

   Note: ``In Old English, generally, thou is the language of a
         lord to a servant, of an equal to an equal, and
         expresses also companionship, love, permission,
         defiance, scorn, threatening: whilst ye is the language
         of a servant to a lord, and of compliment, and further
         expresses honor, submission, or entreaty.'' --Skeat.

   Note: Thou is now sometimes used by the Friends, or Quakers,
         in familiar discourse, though most of them corruptly
         say thee instead of thou.

Thou \Thou\, v. i.
   To use the words thou and thee in discourse after the manner
   of the Friends. [R.]

Source : WordNet®

thou
     n : the cardinal number that is the product of 10 and 100 [syn:
         {thousand}, {one thousand}, {1000}, {M}, {K}, {chiliad},
         {G}, {grand}, {yard}]