Badly means in a way that is poor, inadequate, or not done well. When you perform badly on a spelling test, you get many answers wrong. When a team plays badly, they make mistakes and lose by a large margin. If you treat someone badly, you're being unkind or unfair to them.

The word describes how something is done, not what is done. A talented musician who practiced every day might still play badly if they're sick or nervous. A usually kind person might behave badly when they're angry or tired. The opposite of doing something badly is doing it well.

You can also use badly to mean “very much” or “urgently.” If you badly want to make the soccer team, you want it intensely. If someone is badly injured, they're hurt seriously. In these cases, badly emphasizes how strong or severe something is.