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.n. One who is opposed to some proposed or undertaken course of action, policy, measure, movement, or enactment, as, for example, to imperialism.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.