MUF
material unaccounted for.
Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for muf
Muffle, muf′l, n. the thick naked upper lip and nose, as of a ruminant.
Mufti, muf′ti, n. a doctor or official expounder of Mohammedan law in Turkey: the dress of an officer off duty.