- a landslide of wet volcanic debris on the side of a volcano.
- the deposit left by such a landslide.
- a landslide of volcanic debris mixed with water down the sides of a volcano, usually precipitated by heavy rainfall
- A wet mass of volcanic fragments flowing rapidly downhill. Lahars usually contain ash, breccia, and boulders mixed with rainwater or with river or lake water displaced by the lava flow associated with the volcano.
- The deposit produced by such a flowing mass.