bolt upright

bolt upright (not comparable)

1. Vertical, with the back held stiffly.

   to sit bolt upright; to stand bolt upright

• “bolt upright”, in Cambridge English Dictionary, Cambridge, Cambridgeshire: Cambridge University Press, 1999–present.
• “bolt upright”, in Collins English Dictionary.
• “sit bolt upright”, in Merriam-Webster Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.
• “sit stand bolt upright” in Longman Dictionary of Contemporary English, Longman.