Definition of "back up" [back• up]

• To move backwards, especially for a vehicle to do so. (verb)
• To move a vehicle backwards. (verb)
• To undo one's actions. (verb)
• To reconsider one's thoughts. (verb)
• To copy (data) as a security measure. (verb)

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• "He quickly pulled his hands apart and looked back up to see one of the landing control crewmen, a short, wiry man named Al Dietz, walking toward him."
• "Heading back up the conveyor to the canopy-side transport station?"
• "Climbing back up the steps and continuing west, we find some tumbledown shacks at the top of the path leading to the slipway."