four square 直率的；坦白的

The girl is four square. 这女孩很直率。

on all fours 爬着

The baby was crawling about on all fours. 婴儿那时正在满处爬。

four-lettered words 下流话

These books are full of four-lettered words. 这些书里脏话连篇。

in fours 每组四个

Group together in fours! 每四人一组!

Students are standing in a line，in fours. 学生们每组四人排成队。