WordWeb Online

1. Understand or realize, usually after some time or initial difficulty
   "She didn't know what her classmates were plotting but finally cottoned on";
   - catch on [informal], get wise [informal], get onto, tumble [informal], latch on [informal], twig [Brit, informal], get it, cop on [Brit, informal]

Derived forms: cottoned on, cottoning on, cottons on

Type of: apprehend, compass, comprehend, dig [informal], get the picture, grasp, grok [N. Amer, informal], savvy