Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
contrōversor, āri, v. dep. [controversus], to be at variance one with another, to dispute (very rare): ut inter vos de hujuscemodi rebus controversemini, Cic. Fragm. ap. Prisc. p. 803 P. (IV. 2, p. 477 Orell.): nihil invicem, Sid. Ep. 4, 1.