1) to place one's self in opposition, to oppose, to dispose in turn, to take in hand in turn, to retaliate
Part of Speech: verb
From G473 and G1303; to set oneself opposite, that is, be disputatious: - that oppose themselves.
|be hostile toward||39.1|
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root ἀντιδιατίθεμαι; click on the second column to search for that grammatical form of the root ἀντιδιατίθεμαι; click on the third column to search for that word and grammatical form; click on the total to search for the root ἀντιδιατίθεμαι.