Definitions

1. noun

a small, uncontrolled fire in a forest or woodland, especially one that is difficult to put out

“The underburn in the forest had to be extinguished by the fire department before it spread further.”

2. verb

to burn or set fire to the undergrowth of a forest or woodland, especially to clear it for grazing or to promote new growth

“The farmer decided to underburn the field to create a more open area for their livestock.”