Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
acclīvĭtas, ātis, f. [acclivis], an ascending direction, an acclivity, ascent: pari acclivitate collis, Caes. B. G. 2, 18; so Col. 2, 4, 10.
Concr. of the rising place itself, Amm. 14, 2, 13.