backslash /ˈbækˌslæʃ/noun 2verb 1forms 3 noun2 •The punctuation mark \ (a left-leaning diagonal line). (Common uses include (1) use as a delimiter in filepaths and (2) use as an escape character to mark literals.) •(nonstandard, rare) The punctuation mark /; a slash, forward slash.Also, avoid submenus^([sic]) that can confuse the audience—if you're giving lengthy Web site addresses full of backslashes, shorten it so only the Web site's home page is given. — 2010 verb1 •To escape (a metacharacter) by prepending a backslash that serves as an escape character, thereby forming an escape sequence. formsbackslashed · backslashing · backslashes