WordWeb Online

1. Causing irritation or annoyance
   - annoying, bothersome, galling, irritating, nettlesome, pesky [informal], pestering, pestiferous, plaguy, plaguey, teasing, vexatious, vexing, irksome, dratted [informal]
    
2. [informal] Small and of little importance
   - fiddling [informal], footling [informal], lilliputian [informal], little [informal], niggling [informal], piddling [informal], piffling [informal], petty [informal], picayune [N. Amer, informal], trivial [informal], piddly [informal]

Derived forms: nigglier, niggliest

See also: disagreeable, unimportant