forbidden UK /fəˈbɪdən/US /fɚˈbɪdən/adjective 1forms 2phrases 1 adjective1 •not allowed by a rule or by the person in chargeThis kind of immediate control structure we take to be characteristic of the tribe, and it leads to a rather rigid type of system in which 'every action not mandatory is forbidden'. — 1999 formsmore forbidden · most forbidden Phrases with forbidden forbidden fruitThe fruit forbidden to Adam.