bolt 1 
(bōlt)
(bōlt)n.
1. A bar made of wood or metal that slides into a socket and is used to fasten doors and gates.
2. A metal bar or rod in the mechanism of a lock that is thrown or withdrawn by turning the key.
3. A fastener consisting of a threaded pin or rod with a head at one end, designed to be inserted through holes in assembled parts and secured by a mated nut that is tightened by applying torque.
4.
a. A sliding metal bar that positions the cartridge in breechloading rifles, closes the breech, and ejects the spent cartridge.
b. A similar device in any breech mechanism.
5. A short, heavy arrow with a thick head, used especially with a crossbow.
6. A flash of lightning; a thunderbolt.
7. A sudden or unexpected event: The announcement was a veritable bolt.
8. A sudden movement toward or away.
9. A large roll of cloth of a definite length, especially as it comes from the loom.
v. bolt·ed, bolt·ing, bolts
v.tr.
1. To secure or lock with or as if with a bolt.
2. To arrange or roll (lengths of cloth, for example) on or in a bolt.
3. To eat (food) hurriedly and with little chewing; gulp.
4. To desert or withdraw support from (a political party).
5. To utter impulsively; blurt.
6. Archaic To shoot or discharge (a missile, such as an arrow).
v.intr.
Idioms: 1. To move or spring suddenly.
2. To start suddenly and run away: The horse bolted at the sound of the shot. The frightened child bolted from the room.
3. To break away from an affiliation, as from a political party.
4. Botany To flower or produce seeds prematurely or develop a flowering stem from a rosette.
bolt from the blue
A sudden, shocking surprise or turn of events.
bolt upright
In a rigidly vertical position: sat bolt upright.
[Middle English, from Old English, heavy arrow.]