naive, simple or childish
He made jejune generalizations about how all students were lazy and never did any work.
by Leszek Trojanowski July 14, 2005
1 more definition
The worst word in the English language, jejune just bleeds pomposity and snobbery. If you seriously use jejune in a sentence you a) are automatically an asshole and b) should be slapped across the mouth.
"I detected a jejune air that had not irked me before."- Brideshead Revisited
by Lord Sebastian February 24, 2014