butterfly gate
n.— «The insert was among several in the Nov. 15 issue, celebrating the magazine’s 40th anniversary. All the inserts were what the industry calls butterfly gates—ad pages on the outside, which unfold to reveal pages of articles inside.» —“Antismoking Activist Calls Rolling Stone Insert ’One Great Big Cigarette Ad'” by Stuart Elliot New York Times Nov. 26, 2007. (source: Double-Tongued Dictionary)
Further reading
When Kentrell from West Memphis, Arkansas, worked for a granite company, his co-workers who were about to put two pieces of granite together would say I’m going to pull a seam. But why would they use the word pull for the action of pushing...
You know when a cat’s tail goes straight up and appears to vibrate? Emily from Coventry, Rhode Island, says her family has their own word for that: fribbling. She says her family also made up the word bomple to denote the action of fruit...