Initialism of General Management Committee. (the general committee of a constituency party of the British Labour Party.)
"The candidate was selected by the GMC after months of deliberation within the local constituency branch."
In plain English: GMC is an acronym for General Motors, which makes cars and trucks.
"The GMC truck was parked in front of the diner while they waited for their coffee."
Initialism of General Medical Council.
"The gmc root found in many English words originally came from a common ancestor language."
Abbreviation of Germanic.