1. To spill or slop 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 sloshing over the handrails onto the deck. You need to stop moving so quickly or the soup will end up sloshing over the side of the bowl!
2. Of a liquid, to cover, coat, or drench someone or something as a result of being spilled or splashing onto them or it. The whale performed a massive leap in its tank, and water sloshed over the entire crowd. Wet cement sloshed 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 or splashing it. In this usage, noun or pronoun is used between "slosh" and "over." He was so drunk that he started sloshing his drink all over the people he was dancing with. It looks like they just sloshed tar over the cracked parts of the road, rather than fixing it properly.
slosh something (all) over someone or something
to spill or splash a liquid over someone or something. Laura tripped and sloshed the grape juice all over Martha. Martin sloshed pancake batter over the side of the stove.
[for a liquid] to splash over its container. The water in the wading pool sloshed over and made the grass slippery. Don't fill the glass too full. It will slosh over.