(grammar) A noun that denotes an agent that performs the action denoted by the verb from which the noun is derived, such as "rider" derived from "to ride", or "cutter" derived from "to cut".

A member of an intelligence agency whose identity or affiliation is kept confidential.

Any compound that has an affinity for water such that it will extract it from other materials; a desiccant

A spy who pretends to be a double agent for one side, while actually acting as a double agent for the other side.

A person who secretly disrupts a group's activities from within the group, particularly by encouraging or committing illegal acts to discredit the group or expose them to prosecution; an instigator, troublemaker.

A female agent provocateur; a woman who incites someone to do something, especially something incriminating.

a catalyst

A person who organizes the publicity for a firm or organization, and acts as an intermediary with the press and other media

A potent herbicide and defoliant used by US forces in the Vietnam War.

(chemistry) Any substance that oxidizes, or receives electrons from, another; in so doing, it becomes reduced.