If something is stunted, it's been prevented from growing or developing to its full potential. After a hot, dry summer, there's nothing left in your vegetable garden but a few stunted tomato plants.
Stunted things are scrawny, like the tiny runt in a litter of puppies. A lack of sun in your yard will result in stunted roses and daisies, and malnourishment can lead to stunted growth in humans. People can also be emotionally stunted if they aren't nurtured and encouraged to express their feelings. Stunted comes from the verb stunt, "prevent from growing or developing properly."