WordWeb Online

1. Not important
   "a relatively unimportant feature of the system"; "the question seems unimportant"
    
2. Devoid of importance, meaning, or force
   - insignificant

See also: fiddling, flimsy, footling, fragile, hole-and-corner, hole-in-corner, immaterial, importance, inappreciable, inconsequent, inconsequential, indifferent, inessential, light, lightweight, lilliputian, little, meaningless, nickel-and-dime [N. Amer], niggling, nonmeaningful, petty, picayune [N. Amer], piddling, piddly, piffling, potty [Brit, informal], rinky-dink [N. Amer], significance, slight, small-time, superficial, tenuous, thin, trivial, unessential

Antonym: important