beam
brim
boom
Broom, bloom, bosom.
kim, kilm,kom
It could be malingering.
Words beginning wth M and ending with ING:makingmanagingmarchingmarkingmeaningmeltingmemorizingmentioningmentoringmigratingmissingmixingmovingmunching
mob
isotherm, idealism
monkfish
Unmask? Something un-m..
mate ?
militant, murkiest, movement
nothing unless you want a word that ends with an -ing sound
The word you're looking for is monopoly.