v.1. To depart for some destination: She's heading off to New York City next week. He headed off for the mountains for his annual vacation.
2. To intercept or divert someone or something: Try to head them off before they get home. The sheriff headed off the gangsters at the pass.
3. To block the progress or completion of something: The town headed off the attempt to build another mall. The city council wanted to pass a restrictive zoning ordinance, but the mayor headed them off.