n.; pl. Metatheses [ L., fr. Gr. meta`qesis, fr. metatiqe`nai to place differently, to transpose; meta` beyond, over + tiqe`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. [ 1913 Webster ]

2. (Med.) A mere change in place of a morbid substance, without removal from the body. [ 1913 Webster ]

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. [ 1913 Webster ]