bulla
/ˈbʊlə/noun
(pl. bullae /-liː/ )
1
- Medicine a bubble-like cavity filled with air or fluid, in particular【医】大泡, 大水（或脓）疱, 尤指：
1.1
- a large blister containing serous fluid大（水）疱。
1.2
- an abnormal air-filled cavity in the lung.肺（气肿）大泡。
2
- Anatomy a rounded prominence【剖】圆凸物。
3
- a round seal attached to a papal bull, typically one made of lead（罗马教皇的）印玺（尤指铅制的）。
词源
Latin， literally 'bubble'.