noun

• (originally) A traditional Indian and Persian body massage given after pouring warm water over the body and rubbing it with extracts from herbs.
• (hygiene) A commercial liquid soaplike product for washing hair or other fibers, such as carpets.
  "These endocrine disruptors are everywhere: plastics, shampoos, cosmetics, cushions, pesticides, canned foods and A.T.M. receipts. They often aren’t on labels and can be difficult to avoid."
• (humorous, slang) Champagne.

verb

• (intransitive) To wash one's own hair with shampoo.
  "My neat-freak of a friend has been compulsively shampooing for every bath he has taken."
• (transitive) To wash (i.e. the hair, carpet, etc.) with shampoo.
  "Each pony had his sais, his groom, who lived and ate and slept with the animal, and had betted a good deal more than he could afford on the result of the game. There was no chance of anything going wrong, but to make sure, each sais was shampooing the legs of his pony to the last minute. Behind the saises sat as many of the Skidars' regiment as had leave to attend the match […]"
• (transitive) 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.