Something cheap doesn't cost much money. But watch out, because cheap things are also often cheaply made.
When prices are low, they're cheap: that's a good thing. However, this word is often an insult. Hitting someone who isn't looking is a cheap shot. Things that aren't very well made and use low-quality materials are cheap. When someone — especially a woman — is dressed in a trashy way, people say "You look cheap!" And if you have a stingy Uncle Scrooge in your family, you can call him cheap or even a cheapskate.