The Latin and English form of a Greek preposition, used as a prefix to signify down, downward, under, against, contrary or opposed to, wholly, completely; as in cataclysm, catarrh. It sometimes drops the final vowel, as in catoptric; and is sometimes changed to cath, as in cathartic, catholic.
A prefix of words of Greek origin, meaning down, downward, against, in accordance with, occasionally simply intensive, and often (like English be-) providing a transitive power. See words following. Additionally often kata-.