Definition of Bullous

Bullous: Characterized by blistering, such as in a second-degree burn.

Bullous is the adjective for bulla. A bulla is a blister more than 5 mm (about 3/16 inch) in diameter with thin walls that is full of fluid.

A bulla on the skin is a blister. A bulla on the pleura (the membrane covering the lung) is a bleb.

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