Bullae: More than one bulla, a bulla being a blister more than 5 mm (about 3/16 inch) in diameter with thin walls that is full of fluid.

Blisters on the skin are called bullae. Bullae on the pleura (the membrane covering the lung) are also called blebs.

In Latin a bulla (plural: bullae) was a "bubble, stud or knob." It referred to any rounded protrusion, particularly one that was hollow or cystic.