anti

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A person who is opposed to something, such as a group, policy, proposal, or practice.
2. adj. Opposed: "Douglas MacArthur had a coterie of worshipers, balanced off by an equal number . . . who were vehemently anti” ( Joseph C. Harsch).
3. prep. Opposed to; against.

Century Dictionary and Cyclopedia

1. n. A prefix of Greek origin: originally only in compounds or derivatives taken from the Greek or formed of Greek elements, as in antipathy, antinomy, etc. (the earliest example in English being antichrist, which see), but now a familiar English formative, meaning primarily against, opposed to. It forms — Compound nouns (with the accent on the prefix), in which anti- has the attributive force of opposed to, opponent, opposite, counter, as in antichrist, antipope, antichorus, anticyclone, antipole, etc.
2. n. One who is opposed to some proposed or undertaken course of action, policy, measure, movement, or enactment, as, for example, to imperialism.
3. n. In chem., a prefix used to indicate that two groups or two atoms which might react with each other are so separated in space that they do not readily do this. It is contrasted with the prefix syn-. Thus in antibenzaldoxime, , the H and OH do not readily combine to form water, while in synbenzaldoxime, , such a combination takes place easily.

Wiktionary

1. adj. chemistry Describing a torsion angle between 90° and 180°
2. n. A person opposed to a concept or principle.
3. prep. rare A word used before a noun or noun phrase to indicate opposition to the concept expressed by the noun or noun phrase.

GNU Webster's 1913

1. A prefix meaning against, opposite or opposed to, contrary, or in place of; -- used in composition in many English words. It is often shortened to ant-.

WordNet 3.0

1. n. a person who is opposed (to an action or policy or practice etc.)
2. adj. not in favor of (an action or proposal etc.)