1. a noxious or foul-smelling gas or vapor
Usage: formal; literary
2. a poisonous or pestilential exhalation from the earth
Usage: archaic; geological

Examples

• The mephitis rising from the swamp made it difficult to breathe.
• Ancient Romans believed that mephitis from certain caves could be deadly.
• The miners detected a dangerous mephitis seeping from the rock formations.
• The scientist studied the mephitis emanating from the volcanic vents.
• Local legends warned travelers about the mephitis that plagued the valley.
• The foul mephitis from the industrial site contaminated the surrounding area.