What does it mean if you kill a frog in your dream?

It could mean you was angered in the past few days and your mind is releasing the anger in your dream.

Another possibility is that the dog in your dream symbolizes a person or thing with which you are angry. The dog might well represent something you did that you regret, or a part of yourself that you wish would just disappear. Dogs tend to hang around even after told to go away; in that sense, a dog is a lot like a bad habit. Listen to your dream, and try to figure out what it is in your life that you really would like to get rid of. Then you can take realistic action to correct your situation.