1. To spill or slosh over the side of something as a result of being moved or sloshed around jerkily. The boat was rocking so badly that water has started slopping over the handrails onto the deck. You need to stop moving so quickly or the soup will end up slopping over the side of the bowl!
2. To cover, coat, or drench someone or something as a result of being spilled, splashed, or sloshed. The whale performed a massive leap in its tank, and water slopped over the entire crowd. Wet cement slopped all over the pile of lumber when the wheelbarrow tipped over.
3. To cover someone or something with some liquid as a result of spilling, splashing, or sloshing it. In this usage, a noun or pronoun is used between "slop" and "over." He was so drunk that he started slopping his drink all over the people he was dancing with. It looks like they just slopped tar over the cracked parts of the road, rather than fixing it properly.
slop something over something
to spill or splash some liquid onto something. He slopped the starting fluid over the charcoal and lit it. The artist slopped some grape juice over the canvas and proceeded to spread it around in an artistic fashion.
[for a liquid] to splash out of or overflow a container. The milk slopped over and messed up the carpet. Her cup slopped over and spilled its contents on the kitchen table.