Other forms: spacewalks; spacewalking; spacewalked
When an astronaut gets out of an orbiting spacecraft, she spacewalks. The first person to spacewalk was Soviet cosmonaut Alexei Leonov, who floated outside his capsule in 1965.
The verb spacewalk is precisely what you might imagine: to "walk" in space, drifting in orbit while tethered to a spacecraft. It's also a noun, the name for such an activity: "The first U.S. spacewalk occurred in 1965, when Ed White exited the Gemini spacecraft for 21 minutes." Astronauts today routinely perform spacewalks in order to repair space stations and do other outer-space maintenance tasks.