Initialism of metal matrix composite.
"The researchers tested how adding silicon carbide fibers to an MMC improved the alloy's heat resistance."
In plain English: MMC stands for multi-mode card, which is an older type of memory chip used to store data on devices like phones and cameras before modern flash drives became common.
"The mmc helped fix the broken fence quickly before dinner was ready."
Initialism of Montreal Metropolitan Community.
"The new zoning laws were debated by officials from the Mmc before being passed into effect."