To stand four-square behind someone or something means to be firm in your support of that person or thing.
例句
They stood four-square behind their chief, and they would not accept pressure on him to resign...他们坚决支持自己的领导，而且不允许任何压力迫使其辞职。He was still certain that Franklin was four-square for reform.他还是很确信富兰克林会坚定不移地支持改革。
ADJ
(建筑或结构)方方正正的，方正牢固的
A four-square building or structure is square in shape and looks solid and well-built.
英英词典释义
Noun
1. (geometry) a plane rectangle with four equal sides and four right angles; a four-sided regular polygon;
"you can compute the area of a square if you know the length of its sides"
Adjective
1. characterized by firm and unwavering conviction;
"a foursquare refusal to yield"
Adverb
1. in a square position;
"the building stood foursquare"
2. with firmness and conviction; without compromise;
"he stood foursquare for religious liberty and toleration"- C.G.Bowers"dealt straightforwardly with all issues"