Definitions for "Mop-up"
Making an area safe again after the fire is brought under control. This includes extinguishing or removing burning material along the fire line.
Final stage of fire fighting—digging up all roots and burning material; putting out the last of all embers and coals.
After the fire has been controlled, all actions required to make the fire "safe", prior to being called out. This includes trenching, falling snags, and checking all control lines.