1. Lacking courage or vitality
   "he was a yellow wishy-washy worm";
   - gutless, namby-pamby [informal], spineless
    
2. Lacking interest, significance or impact
   "a wishy-washy personality";
   - insipid, jejune
    
3. Lacking in vibrancy, colour, force, or decisiveness
   "The politician gave a wishy-washy answer to the question";
   - weak, indecisive

See also: lame, lameo [informal], meh [informal], uninspiring, uninteresting

Encyclopedia: Wishy-washy