Burn Down

1. When someone uses fire to destroy a structure.

Examples: One of our neighbors threatened to burn his house down.
The firemen burned down an old house to practice fighting fires.

2. When a house, building or other structure is completely destroyed as a result of fire.

Examples: By the time the firemen arrived, half of the building had already burned down.
A lot of buildings were burned down in the Great Chicago Fire of 1871.

See our complete list of English phrasal verbs.