WordWeb Online

1. Lacking in nutritive value
   "the jejune diets of the very poor";
   - insubstantial
    
2. Displaying or suggesting a lack of maturity
   "jejune responses to our problems";
   - adolescent, juvenile, puerile
    
3. Lacking interest, significance or impact
   "jejune novel";
   - insipid

See also: immature, meh [informal], uninspiring, uninteresting, unwholesome

Encyclopedia: Jejune