bolt upright


Precisely perpendicular, erect in carriage, as in She sat bolt upright in her pew. This expression was used in slightly different form by Chaucer in the late 1300s: “She was ... long as a mast and upright as a bolt” (The Miller's Tale).

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.