Fort/fɔːrt/ Definition 1 of 4Pro Tip 1/3Historical Use The term has a military origin, usually referring to a secure place for troops. The ancient fort had walls thick enough to withstand sieges. Pro Tip 2/3Figurative Sense Sometimes used to imply that someone is defensive or hard to approach emotionally. He put up a fort around his heart after the breakup. Pro Tip 3/3Cultural Heritage Forts can be historic landmarks and tourist attractions today. We visited the fort, which has been a museum for a century.