backlineEnglishOxford Dictionary of Englishbackline /ˈbaklʌɪn / ▸ noun 1 the defensive players lined up across the field in sports such as soccer and rugby: Robinson was left with limited options across his backline he came on to bolster Liverpool's backline. 2 a line marking the back of something, especially the area of play in a game. 3 the amplifiers used by a popular music group for guitars and other instruments, typically placed across the back of the stage.