Sheep dipping is disguising a spy's identity with a day job.

Spies have their own secret language to keep from being discovered. By spying on these spies, we've managed to uncover the meaning of some of their terms.

1. Black Bag Job

A black bag job, or black bag operation, is a covert entry into a building to plant surveillance equipment or find and copy documents, computer data, or cryptographic keys. The name is derived from the black bags spies used to carry the equipment for such operations. In 1972, the Supreme Court declared black bag jobs unconstitutional, but are bags of different colors okay?

2. Brush Contact

A brush contact is a brief and public meeting in which two spies discreetly exchange documents, funds, or information without speaking to each other, except perhaps to utter "Excuse me" or other pleasantries. To the average person, the interaction would seem like an accidental encounter between two strangers.

3. L-Pill

An L-pill is a lethal pill carried by spies to prevent them from revealing secrets if captured and tortured. During World War II, some L-pills contained a lethal dose of cyanide encased in a glass capsule that could be concealed in a fake tooth and released by the agent's tongue. If he bit into the capsule and broke the glass, he would die almost immediately. But if the pill came loose and was swallowed accidentally while the agent was sleeping or chewing gum, it would pass through his system without causing any harm, as long as it didn't break and release the poison.

4. Window Dressing

The best spies are able to blend into any situation. To accomplish this, they use window dressing -- the cover story and accessories they use to convince the authorities and casual observers that they are everyday people and not spies. For example, if a spy is disguised as a construction worker to cover the fact that he is planting a listening device, his window dressing might include official-looking work orders, tools, and knowledge of the people who would have authorized his presence.

5. Sheep Dipping

In farming, sheep dipping is a chemical bath given to sheep to rid them of bugs or disease or to clean their wool before shearing. In CIA terminology, sheep dipping means disguising the identity of an agent by placing him within a legitimate organization. This establishes clean credentials that can later be used to penetrate adversary groups or organizations. Similar to the real sheep, the agent is cleaned up so that nobody knows where he's been, kind of like money laundering.

If you're going to communicate in the field, there are a few more terms used by spies that you should know. Read about them on the next page.