WordWeb Online

1. Worry unnecessarily or excessively
   "don't niggle too much over the grandchildren--they are quite big now";
   - fuss, fret
    
2. Argue over petty things
   "Let's not niggle over pennies";
   - quibble, pettifog, bicker, squabble, brabble

Derived forms: niggled, niggling, niggles

Type of: argue, contend, debate, fence, sweat [N. Amer, informal], worry

Encyclopedia: Niggle