Learner's definition of VOLCANO
: a mountain with a hole in the top or side that sometimes sends out rocks, ash, lava, etc., in a sudden explosion (called an eruption)
The volcano last erupted 25 years ago.
an active volcano [=a volcano that could erupt at any time or that is erupting now]
a dormant volcano [=a volcano that is not currently active]
an extinct volcano [=a volcano that does not erupt anymore]