Bulla \Bul"la\, n.; pl. Bull[ae]. [L. bulla bubble. See Bull an edict.]

1. (Med.) A bleb; a vesicle, or an elevation of the cuticle, containing a transparent watery fluid.

2. (Anat.) The ovoid prominence below the opening of the ear in the skulls of many animals; as, the tympanic or auditory bulla.

3. A leaden seal for a document; esp. the round leaden seal attached to the papal bulls, which has on one side a representation of St. Peter and St. Paul, and on the other the name of the pope who uses it.

4. (Zo["o]l.) A genus of marine shells. See Bubble shell.

Source: Webster's Revised Unabridged Dictionary (1913)