think ‧ a ‧ ble /ˈθɪŋkəb ə l/ BrE AmE adjective [not before noun]
[ Word Family: noun : ↑ think , ↑ rethink , ↑ thinker , ↑ thinking , the unthinkable; verb : ↑ think , ↑ rethink ; adjective : ↑ thinkable ≠ ↑ unthinkable , ↑ thinking ≠ ↑ unthinking ; adverb : ↑ unthinkingly ]
able to be thought about or considered SYN possible :
At that time, it would not have been thinkable to openly criticize the government.