名詞 foldout:

1. an oversize page that is folded in to a book or magazine
   同義詞：gatefold

fold.out

n.（名詞）
Printing A folded insert or section, as of a cover, whose full size exceeds that of the regular page.
【印刷術(shù)】 折頁(yè)：折疊起來的插入物或部分，比如尺寸超過了一般的書頁(yè)尺寸的畫頁(yè)
A piece or part, as of furniture, that folds out or down from a closed position.
折頁(yè)：如家具的一塊或一部分，可以從合起的位置折出來或折下去

【引伸】
fold.out.
adj.（形容詞）