A style first pooh-poohed by Alexander Pope in his 1727 treatise against dunces, Peri Bathous; or the Art of Sinking in Poetry, bathos is when an author seems to be trying really, really hard to write about something lofty or noble or elevated, but then descends into the trivial and/or stupid.
Think of bathos as an abrupt shift in tone from high to low. Bathetic style can be unintentional or used for comedic effect, as in this famous line from Douglas Adams's The Hitchhiker's Guide to the Galaxy:
Why are people born? Why do they die? And why do they spend so much of the intervening time wearing digital watches?