1. [informal] Alert, aware, and up-to-date with current trends
   "The new marketing director is really with it";
   - with-it [informal]
    
2. Having the shrewd resourcefulness needed to survive in an urban environment
   "The with it teenager knew all the street smarts";
   - streetwise, street-smart, with-it [informal]
    
3. In accord with the most fashionable ideas or style
   "with it technology";
   - up-to-date, up to date, cutting-edge, with-it [informal], nouveau

See also: fashionable, hip [informal], smart, stylish