Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
summĭtas, ātis, f. [summus], the highest part, height, top, summit (post-class.): placidioribus locis septem pedibus summitas vitis insurgit, Pall. 1, 6, 10; Macr. Somn. Scip. 1, 6 med.: terrae, Censor. de Die Nat. 13: deum summitatem omnium summorum obtinentem, Arn. 1, 13; App. Dogm. Plat. 2, p. 15, 7; Amm. 15, 10, 6 (not Plin. 37, 9, 37, § 118, where Jan. reads imitata).