Onlar yan yana yürüyordu. - They were walking two abreast.
Bu ikisi yan yana duruyor. - These two are standing abreast.
English - English
Definition of abreast of in English English dictionary
being up to particular standard or level especially in being up to date in knowledge; "kept abreast of the latest developments"; "constant revision keeps the book au courant"; "always au fait on the latest events"; "up on the news"
If people or things walk or move abreast, they are next to each other, side by side, and facing in the same direction. The steep pavement was too narrow for them to walk abreast