Source : Webster's Revised Unabridged Dictionary (1913)

Shampoo \Sham*poo"\, v. t. [imp. & p. p. {Shampooed}; p. pr. &
   vb. n. {Shampooing}.] [Hind. ch[=a]mpn[=a] to press, to
   squeeze.] [Writing also {champoo}.]
   1. To press or knead the whole surface of the body of (a
      person), and at the same time to stretch the limbs and
      joints, in connection with the hot bath.

   2. To wash throughly and rub the head of (a person), with the
      fingers, using either soap, or a soapy preparation, for
      the more thorough cleansing.

Shampoo \Sham*poo"\, n.
   The act of shampooing.

Source : WordNet®

shampoo
     n 1: cleansing agent consisting of soaps or detergents used for
          washing the hair
     2: the act of washing your hair with shampoo
     v : use shampoo on (hair)