As far as we know, no dictionary lists busstop. Spelling bus stop as a single word would make sense because many similar pairs have fused into compounds (e.g., stoplight, snowman, headstone), but bus stop has never gone this route, perhaps because the two s‘s would be awkward.
Examples
We found only a few scattered examples of busstop in current news sources. Most publications go with the two-word bus stop—for example:
Then the grandma from our hotel kindly shows us how to get to the bus stop … [Washington Post]
Meanwhile the group will be selling local vegetable bags at the King’s Buildings bus stop this afternoon. [The Guardian]
She ran away one afternoon, but the headmistress intercepted her at the bus stop. [Globe and Mail]
… a snow-covered Lexus SUV, parked squarely in the middle of a bus stop. [Boston Globe]
