Not interesting, dull, empty. Also childish and lacking in nutrition.
Lexically speaking, dated back to the 1600’s, this interesting adjective stems from the Latin ieiunus, meaning empty, dry or barren.
But it also stems from an older word, coined some 200 years earlier (in the late 14th century) originating in the same Latin root, the word jejunum, which is the middle section of the small intestine in the most higher vertebrates such as mammals, reptiles and birds. The jejunum earned its name following the fact that it is always found empty in dissections (as it tends to drain in a body laid on its back).
Why this word?
This is a great word as it is a one specific adjective, stemming from a specific physical occurrence that grew to describe not only that, but also anything else that is lacking in content.
How to use jejune?
Simply, as an adjective synonymous to empty. When you read a long article and upon finishing it you learn that you haven’t learned a thing, that article can be called jejune. After spending time with a person who seems to have no inner world, no interests or added value to his words, you can describe his personality as jejune.
And of course, when you are extremely hungry, you are jejune as well.