Wiktionary
mud room
n. A room used to act as a barrier between outdoors and indoors.
Usage examples of "mud room".
The entryway of the inn was a conventional mud room, barely lit by an overhead lamp.
She'd ordered the oldest, a surly thing who was way too big for his filthy britches, into the mud room off the garage.
At the end of the hall was a narrow, spiral staircase that led down to the mud room.