Playfully jocular; humorous.
Joking or trying to be jocular, esp. at an inappropriate time.
The definition of facetious is a joke made about something serious.
An example of facetious is someone saying that people whose homes have burned down don't have to worry about whether the housekeeper did a good job.
Robbie's joke about Heather's picture was just him being facetious.
Origin of facetious
French facétieux from facétie jest from Latin facētia from facētus witty