Fatuous is an adjective that describes something or someone as absurd or brainless. It comes from the Latin word for foolish. The adverb form is fatuously and the noun form is fatuousness.
Facetious is also an adjective. It describes something or someone as being deliberately casual or silly in serious matters and with inappropriate humor. Good synonyms are flippant, glib, and tongue-in-cheek. The adverb form is facetiously and the noun form is facetiousness.
It should be noted that most of the time facetious is used simply to denote that something was meant to be a joke or not to be taken seriously. It does not usually carry the ‘inappropriate for serious matters’ part of the definition. Facetious is preferred almost three to one over fatuous.
“The glass roof is a fatuous architectural flight of fancy, in my view,” Martin said. [Ottawa Citizen]
Karen is so fatuously self-centered and compulsively brand-name-branding that she’s never met a product or a campaign that she wouldn’t endorse. [The New York Times]
But fun turns to fatuousness as the past rears its messy head, leaving the movie to wrestle clumsily with estranged sons, schizophrenic twins, and a frankly inexplicable Anne Heche. [The Guardian]
Video blogger Ahmed Anwar said he received a six-month jail sentence in January 2014 for posting a facetious item on YouTube, mocking the Interior Ministry. [Reuters]
On Wednesday Trudeau facetiously asked if we’d be going into other places like Yemen or go after Boko Haram. [Toronto Sun]
“Hits a new low in condescending facetiousness, with no fewer than 15 performers of varying talents, tongues firmly in cheeks, undercutting all the genre’s action conventions while camping up a storm on two continents,” Andrew Sarris wrote in the New York Observer. [Huffington Post]