Lewis & Short

Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.

prŏpylaeum (-laeon), or prŏpy-lon, i, n., = προπύλαιον, a gateway, entrance; esp. (in plur.) of the celebrated entrance to the temple of Pallas in the citadel of Athens, the Propylœum: Phalereus Demetrius Periclem vituperat, quod tantam pecuniam in praeclara illa propylaea conjecerit, Cic. Off. 2, 17, 60: propylaea nobilia. id. Rep. 3, 32, 44.
In sing.: cum Athenis propylaeon pingeret, Plin. 35, 10, 36, § 101 (al. propylon); 36, 5, 3, § 10.