Other forms: lairs
A lair is a wild animal's den. If you ever find yourself in a forest and face to face with a bear trying to lure you into his lair, beware! He may be plotting to eat you.
The noun lair has its roots in the Old English leger, meaning "bed; place where one lies down." It eventually became the word for an animal's den in the early 15th century. A person can have a lair, too. An evil genius might have a lair where he plots his next crime, for example, while a less scary person might have a cozy lair lined with plush carpet and shelves of books.