meta- or met- cf prefix [NL & ML, fr. L or Gk; L, change, fr. Gk,
among, with, after, change, fr. me]ta among, with, after; akin to OE
mid, mith with, OHG mit

1a: occurring later than or in succession to : after {metestrus}

1b: situated behind or beyond {metencephalon} {metacarpus}

1c: later or more highly organized or specialized form of {Metazoa}

2: change : transformation 

3: more comprehensive : transcending {metaphychology} - used with the
name of a discipline to designate a new but related discipline
designed to deal critically with the original one {metalanguage}

4a: isomeric with or otherwise closely related to {metaldehyde}

4b: involving substitution at or characterized by two positions in the
benzene ring that are separated by one carbon atom 4c: derived from by
loss of water {metaphosphoric acid}