•
Malaysian movement control order, a lockdown measure by Malaysia during COVID-19 pandemic •
Managed Care Organization •
Manitoba Chamber Orchestra •
Manufacturer’s Certificate of Origin •
Marine Corps Order •
Mars Climate Orbiter •
MC Oran, an Algerian association football club •
MC Oujda, a Moroccan association football club •
MegaCon Orlando, a large fan convention in Orlando •
Millennial Choirs and Orchestras •
MinecraftOnline, a
Minecraft multiplayer server •
Miscellaneous Charges Order, a coupon used to process the payment of travel arrangements •
Modern Chess Openings, a reference book on chess openings •
Moscow Chamber Orchestra •
Motorsport Club of Ottawa •
Motor City Online, a massively multiplayer online racing game • Member,
College of Organists, an honorific ==Codes==