Lewis Short
pētro (noun M) : 1. petra.
* A rustic: petrones rustici fere dicuntur, etc.,Fest. p. 206, 23 Müll.; cf.: petrones rustici a petrarum asperitate et duritiā dicti, Paul. ex Fest. p. 207, 6 ib.
* An old wether, whose flesh is as hard as a stone (anteclass.), Plaut. Capt. 4, 2, 40.
Charlton T. Lewis, Charles Short, A Latin Dictionary