If you belittle someone or make them look small, you put them down. You might make a sarcastic comment about someone’s suggestion and this puts them down.
John called his wife an idiot for scratching the car. This really put her down.
A put down is a word, phrase or comment that makes someone feel bad. If someone is wearing clothes that you don’t like and you want to hurt them, you might say:
Nice jacket. I remember when it was in fashion.