Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ae, see the letter A.
Crabra (ae) aqua, an aqueduct or water conduit that extended from Tusculum to the Tiber, Cic. Agr. 3, 2, 9; id. Fam. 16, 18, 3; Front. Aquaed. 9.