1. 幼稚的；不成熟的；头脑简单的
If you describe something or someone as jejune, you are criticizing them for being very simple and unsophisticated.

2. 枯燥乏味的；单调的
If you describe something or someone as jejune, you mean they are dull and boring.

1. lacking interest or significance or impact

e.g. an insipid personality
jejune novel

Synonym: insipid

2. displaying or suggesting a lack of maturity

e.g. adolescent insecurity
jejune responses to our problems
their behavior was juvenile
puerile jokes

Synonym: adolescentjuvenilepuerile

3. lacking in nutritive value

e.g. the jejune diets of the very poor

Synonym: insubstantial