IOM is the written short form of the Isle of Man, a small island in the Irish Sea, between Britain and Ireland. It is close to the United Kingdom and tied to the British Crown, but it is not part of the UK: the people there have their own government, their own laws, and an old language called Manx. You will see IOM on forms, addresses, sports lists, and sometimes on luggage tags. The island is famous for a very fast motorcycle race. Though actually, people almost never say the three letters out loud as a name; when they talk, they say “the Isle of Man.” And the same three letters can mean other things in other jobs — a medical body, a computer term — so this entry is only the island. Look at the rest of the sentence, and you will know which IOM you have.