Noun
The sauce used on Big Mac hamburgers. Synonym of special sauce.
(by extension) Any similar-tasting sauce used on burgers. Synonym of burger sauce. (Can we add an example for this sense?)
Source: en.wiktionary.orgDescribing how they make their iconic burger, said it's made up of 'two beef patties, the bun, Big Mac sauce, dill pickles, onions, shredded iceberg lettuce'. Source: Internet