Definition of bulla
noun (plural bullae /ˈbo͝olē/)
1 Medicine a bubblelike cavity filled with air or fluid, in particular. a large blister containing serous fluid. an abnormal air-filled cavity in the lung.
[ early 19th century]
2 Anatomy a rounded prominence.
[ mid 19th century]
3a round seal attached to a papal bull, typically made of lead.
[ Middle English]