It is called a mmmmmm I don't know
Mogul.
milkmochamulletmoatmummy
mug
egoism
mistime
magic or mystical
mirage
marvellous
· missile · mortar
meter
marathon
Words beginning wth M and ending with ING:makingmanagingmarchingmarkingmeaningmeltingmemorizingmentioningmentoringmigratingmissingmixingmovingmunching