Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† antĭthĕsis, is, f., = ἀντίθεσις, a gram. ng., the putting of one letter for another (e. g. olli for illi, impete for impetu), Charis. p. 249 P.; Diom. p. 437 P.