1. (n.) A prefix meaning between, with, after, behind, over, about, reversely; as, metachronism, the error of placing after the correct time; metaphor, lit., a carrying over; metathesis, a placing reversely.

2. (n.) Other; duplicate, corresponding to; resembling; hence, metameric; as, meta-arabinic, metaldehyde.

3. (n.) That two replacing radicals, in the benzene nucleus, occupy the relative positions of 1 and 3, 2 and 4, 3 and 5, 4 and 6, 5 and 1, or 6 and 2; as, metacresol, etc. See Ortho-, and Para-.

4. (p. p.) Having less than the highest number of hydroxyl groups; -- said of acids; as, metaphosphoric acid. Also used adjectively.