Definition of Bullae

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.

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.