1. Of a liquid, to flow out of a container or over some barrier and onto some person, place, or thing. Don't fill the saucepan too full, or the soup will spill over on the hotplate when it starts to boil. The floodwaters rose above the embankment and spilled over onto the adjacent fields.

2. To spread to and affect another person or thing. He had an infectious cheerfulness that spilled over on those around him. The stress I'd been feeling at work had started spilling over onto other areas of my life, so I knew it was time to make some changes.

3. To go beyond the borders or parameters of something and onto something else, especially due to growing too large in size, amount, or scope. There were so many books piled on top of each other that they had begun spilling over onto other shelves. I share a desk with my coworker, and all the junk he piles up around his computer inevitably spills over on my workspace.