1. To lose weight: This is the most common meaning of "abnehmen". For example, "Ich möchte abnehmen" means "I want to lose weight".
2. To take off (clothing): This meaning is less common, but it can be used to describe removing an item of clothing. For example, "Sie nahm ihren Mantel ab" means "She took off her coat".
It's important to consider the context of the sentence to determine the correct English translation.