Lewis Short
pĕtăsus (noun M) = πέτασος:
* A travelling hat or cap, with a broad brim (cf.: pileus, cucullus).
* Lit., Plaut. Ps. 2, 4, 45; 4, 7, 90; id. Am. prol. 143; Arn. 6, 197.
* Transf., something in the shape of a cap, placed on a building, a cap, cupola, Plin. 36, 13, 19, § 92.
Charlton T. Lewis, Charles Short, A Latin Dictionary