If something starts out serious and then turns trivial, that’s bathos. If you’re watching a serious drama about Poland’s transition to capitalism and it suddenly ends in a giddy car chase, you might remark on the film’s unexpected bathos.
The word bathos came into English in the 17th century from the Greek word bathos, which literally means “depth.” In the 18th century English poet Alexander Pope gave the word its current meaning of a descent from lofty to trite. We often use it for movies or books. Bathos is usually unintentional — which means you can laugh at it. Bathos can also be used more broadly for something that’s trite or overly sentimental.