cat flap

kissanluukku Small hinged panel, usually cut into a door, with an opening just big enough for a cat to enter.
1984, Arthur Hailey, Strong Medicine, Doubleday, ISBN 0385180144, http://books.google.com/books?vid=ISBN0385180144&id=L3QpoNhE90IC&q=%22in+a+rear%22+inauthor:Hailey+date:1984-1984&dq=%22in+a+rear%22+inauthor:Hailey+date:1984-1984&num=100&pgis=1 p. 340,

Then, one Saturday when Martin was working but Yvonne wasn't, she brought a saw and other tools with which she constructed a hinged "cat flap" in a rear down-stairs door. It meant that the cats were free to come and go at any time, the effect being healthier for the pets and for the household.

Jane had sealed up the cat flap, closed the ever-open window of the laundry, but there the cat somehow managed to be, staring up with a look of dependence.

I let the cats out because they couldn't be arsed going through the cat flap. They were just sitting in front of the cat flap and yowling.