rat

Someone who works (or provides workers) during a strike.

A person who is deemed to be despicable or contemptible.

“kill the rat”

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.

Employ scabs or strike breakers in.

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

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.