1 [count] : a bright line of light that appears in the sky during a storm : a flash of lightning
▪ a bolt of lightning = a lightning bolt — often used figuratively in the phrases a bolt from the blue and a bolt out of the blue ▪ The news of his firing came as/like a bolt from the blue. [=like a bolt of lightning from the sky; it was surprising and unexpected] 2 [count] a : a sliding bar that is used to lock a door or window
b : the part of a lock that is moved by a key — see also dead bolt 3 [count] : a long, round piece of metal that has a wider part at one end and is like a screw at the other end ◊A bolt and a nut are used together to hold something in place. — see picture at carpentry; see also nuts and bolts at nut 4 [singular] Brit : the act of running or moving quickly and suddenly in a particular direction or to a particular place
▪ When he saw the police, he made a bolt for [=made a dash for] the door. ▪ The thief made a bolt for it. [=ran away] 5 [count] : a large roll of cloth 6 [count] : a tube-shaped metal part inside a gun 7 [count] : a short, heavy arrow that is shot from a type of weapon (called a crossbow) used mainly in the past ◊If you have shot your bolt, you have done or used everything possible to try to do something, and there is nothing more that you can do.
▪ The team had shot its bolt in the first quarter and didn't score again.