What does MUF stand for?

Makeup Feed - Boiler

Marine Fabricators, Hobe Sound, FL - Manufacturer code for watercraft hull identification number (USCG)

Marksmanship Under Fire (SAUS)

Material Unaccounted For - Nuclear energy

Maximum Usable Frequency - Signal transmission

Muffler

Munivest Fund, Inc. - AMEX symbol (COMM)

Muting - Indonesia - Airport symbol (OAG)