termination shock

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An outer region of the solar system, about 8 billion miles (12.8 billion kilometers) from the Sun, where a standing shock wave is generated as the solar wind, encountering the interstellar medium, slows to subsonic speeds.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun astronomy the boundary marking one of the outer limits of the Sun's influence, where the solar wind dramatically slows
• noun astronomy by extension, that point for space around any star