Other forms: bolts, bolted, bolting
A bolt is a thick metal pin with a screw thread down it, pushed through two things and tightened with a nut so neither can move. The bolts holding a bench to the concrete; the bagful you tip out on the carpet when a wardrobe arrives in a flat box.
The word then runs in two directions. The metal one: the bolt on a door is the bar you slide across at night, so you bolt the door and the door is bolted, nuts and bolts means the practical detail of a thing, and a bolt of cloth is a whole roll of it. The sudden one: a horse bolts when something frightens it and it goes flat out with nobody steering, and a child bolts for the door at the end of a lesson. A bolt of lightning arrives in that same instant, which gives a bolt from the blue — news with no warning in front of it. Bolt your food and you have eaten far too fast; sit bolt upright and you are suddenly straight-backed and wide awake.
1nounboltA thick metal pin, tightened with a nut, that fastens two things together.
“The bench is held down by four heavy bolts.”
2nounbarA bar that slides across to lock a door.
“She slid the bolt across and went to bed.”
3verbhorseTo run off suddenly and fast, with no control.
“The horse bolted the moment the gate opened.”
synonyms: dash, flee
4nounflashA flash of lightning.
“A bolt lit the whole field for a second.”
5verbfastenTo fasten things together with thick metal pins and nuts.
“The shelves are bolted to the wall, so they cannot tip over.”
Too few real examples of this word to estimate which sense is commonest.
Old English had bolt, from Proto-Germanic *bultaz, and perhaps from a root meaning to knock or to strike — Lithuanian still says beldu for I knock, and calls a pole for striking a baldas. The lightning sense reaches back into prehistory: many cultures held that lightning was caused by bolts, darts or stones hurtling down from the sky to the earth, and that belief was still regarded as commonplace until at least 1929.
Old English
bolt
Middle English
bolt
English, today
bolt
From Middle English bolt, from Old English bolt. From Middle English bolt, from Old English bolt, from Proto-West Germanic bolt, from Proto-Germanic bultaz, perhaps from Proto-Indo-European bʰeld- (“to knock, strike”). Compare Lithuanian beldu (“I knock”), baldas (“pole for striking”). Akin to Dutch and West Frisian bout, German Bolz or Bolzen, Danish bolt, Swedish bult, Icelandic bolti. The association of thunder and lightning with 'bolts' is found back into prehistory in many cultures, at least in Eurasia. It comes from the long-standing widespread belief that lightning was caused by bolts, darts, or stones hurtling down from the sky to the earth. This belief was still regarded as commonplace until at least 1929.
Etymology from Wiktionary, CC BY-SA