Ring a bell is an idiom that means to sound familiar or to bring something to mind. Its antonyms include "unfamiliar," "obscure," "unknown," "forgettable," and "ambiguous." Some other antonyms could be "inapplicable," "irrelevant," "unpertinent," and "unrelated." If something doesn't ring a bell, it might be because it is new or unfamiliar to someone, or because it doesn't hold any significance or importance in their memory. Using antonyms for "ring a bell" can help to express that something is not familiar or recognizable to someone, or that it doesn't evoke any memories or associations.