From Longman Dictionary of Contemporary Englishcat flapˈcat flap British English, pet door American English noun [countable] DHPa small hole cut into a door and covered with wood or plastic that moves to allow a pet cat to enter or leave a house
Examples from the Corpus
cat flap• I hear the thump of the cat flap as Cat O'Fun tumbles through it without the feline grace of his fellows.• Became confident and prised the cat flap open again.• Somebody had left me a note, though, through the cat flap in my flat door.• It's only a matter of time till he learns to use the cat flap. 