Look up effusion in Wiktionary, the free dictionary.

Effusion is the process of gases passing through a small hole.

Effusion may also refer to:

Medicine

The seeping of fluid into a body cavity, the fluid itself, or an abnormal collection of fluid in a body cavity or space:

• Ascites
• Pericardial effusion
• Pleural effusion
• Joint effusion
• Subdural Effusion
• Mastoid Effusion
• Knee effusion
• Sometimes called "hydrops"

Geology

• Effusive eruption, an effusion of lava from a volcano