1. past tense of highjack; to seize control of a vehicle (especially an aircraft) by force or threat, typically for ransom or to reach a different destination
Usage: also spelled 'hijacked'; commonly used in news and security contexts
2. to take over or redirect something (such as a conversation, process, or account) without authorization
Usage: figurative or extended use; informal

Examples

• The plane was highjacked by armed passengers who demanded to be flown to a different country.
• Terrorists highjacked the flight and held the crew hostage for several hours.
• Someone highjacked his email account and sent spam to all his contacts.
• The meeting was highjacked by a group of protesters who wanted to discuss their concerns.
• Hackers highjacked the website and replaced it with their own message.
• The conversation was highjacked when she suddenly brought up a completely different topic.