Lewis Short
(verb) : pustŭlo, āvi, ātum, 1, and n. pustula.
* Act., to blister, to cause blisters or pustules; hence, mid., to blister, become blistered: ne usta pustulentur,Cael. Aur. Tard. 5, 1, 16.
* Neutr., to blister, break out into blisters, Tert. Hab. Mul. 6.
Charlton T. Lewis, Charles Short, A Latin Dictionary