1) A trashy person with a pretty mouth that is fun to "splash" or "cum" in.
2) Some one who enjoys catching hot loads with their mouth and or face.
Jessica is just a splash mouth who cares what she likes on her pizza she's probably already full anyways.
When you are so thirsty and take a sip of water and your lips don’t hit the glass you just splash mouthed
You are talking to a room full of people after drinking a large glass of water and you just spray everyone you have just splashed mouth
When Steve got up to the staged he splash mouthed before beginning his set as lead singer of his band