To stop believing (in someone or something); to become disillusioned, embittered, or doubtful (about something or someone). (When said simply as "lose faith," it is often in reference to losing religious faith in God.) The staff have started losing faith in John's ability to manage the restaurant properly. I lost my faith in my friends ever since they turned their backs on me when my husband left. It's not uncommon to lose faith at some point in one's life, but God will reveal himself to you if you're willing to receive Him.