WordWeb Online

1. Not worthy of notice
   - undistinguished
    
2. Signifying nothing
   "insignificant sounds"
    
3. Of little importance or influence or power; of minor status
   "a minor, insignificant bureaucrat"
   - peanut
    
4. Devoid of importance, meaning, or force
   - unimportant

See also: flimsy, fragile, hole-and-corner, hole-in-corner, inappreciable, insignificance, insignificantly, light, meaningless, minor, nonmeaningful, significance, slight, superficial, tenuous, thin, trivial, unimportant, unnoticeable

Antonym: significant