Me*tath"e*sis (?), n.; pl. Metatheses (). [L., fr. Gr. meta`thesis, fr. metatithe`nai to place differently, to transpose; meta` beyond, over + tithe`nai to place, set. See Thesis.]
1. Gram.
Transposition, as of the letters or syllables of a word; as, pistris for pristis; meagre for meager.
2. Med.
A mere change in place of a morbid substance, without removal from the body.
3. Chem.
The act, process, or result of exchange, substitution, or replacement of atoms and radicals; thus, by metathesis an acid gives up all or part of its hydrogen, takes on an equivalent amount of a metal or base, and forms a salt.
© Webster 1913.