a prefix meaning “down,” “against,” “back,” occurring originally in loanwords from Greek (cataclysm; catalog; catalepsy); on this model, used in the formation of other compound words (catagenesis; cataphyll).
from Gk. kata-, before vowels kat-. Its principal sense is "down," but with occasional senses of "against" or "wrongly." Also sometimes used as an intensive. Most Eng. words with this prefix were borrowed through L. after 1500; e.g. catalectic (1589) "wanting a syllable in the last foot."