If you slap someone, you hit them with the palm of your hand.

If you slap someone on the back, you hit them in a friendly manner on their back.

If you slap something onto a surface, you put it there quickly, roughly, or carelessly.

If journalists say that the authorities slap something such as a tax or a ban on something, they think it is unreasonable or put on without careful thought.

If you describe something that someone does as a slap in the face, you mean that it shocks or upsets you because it shows that they do not support you or respect you.

A slap on the wrist is a warning or a punishment that is not very severe.