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

Effusion may also refer to:

Medicine[edit]

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[edit]

• Effusive eruption, an effusion of lava from a volcano