Rat

a person who is deemed to be despicable or contemptible

someone who works (or provides workers) during a strike

one who reveals confidential information in return for money

any of various long-tailed rodents similar to but larger than a mouse

a pad (usually made of hair) worn as part of a woman's coiffure

take the place of work of someone on strike

give away information about somebody

catch rats, especially with dogs

desert one's party or group of friends, for example, for one's personal advantage

employ scabs or strike breakers in

give (hair) the appearance of being fuller by using a rat