Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mĕlĭōro (no perf.), ātum, 1, v. a. [melior], to make better, to better, improve (postclass.): meliorare proprietatem, Dig. 7, 1, 13: melioratum praedium, Cod. Just. 5, 71, 16; Cassiod. Var. 9, 3.