Several things are referred to as “squibs.” In explosives, a squib is a small explosive device which works almost like a miniature stick of dynamite. The term is also used more generally to refer to deceptively small things, like an explosive comment in a conversation or a small sailboat which can be used for high speed racing. For fans of the Harry Potter novels, a squib is a child born to a magical family who lacks magical ability; the term is taken from an English slang phrase, “squib,” which refers to a firework which fails to ignite.
In the sense of explosives, a squib is a small tube packed with an explosive charge. It can be detonated with a fuse or a remote control, depending on how it is wired. Despite the small size, a squib can pack a serious explosive punch which makes it extremely useful. Early squibs were used to detonate cannons, since their smaller charge could rapidly ignite the powder in the cannon, firing the cannonball.
There are other uses for squibs. These small explosives can cause a rapid expansion of gases, for example, and they are the force behind air bags in cars. Squibs are also used in special effects for film and stage; one common use of squibs is as fake bullets which will explode blood packs worn by actors to make it look as though the actor has been hit. Fireworks professionals may also use squibs in the course of their work, as will other explosive experts.
Squibs also pop up in some interesting places. They are the power behind ejection seats in military aircraft, for example, and they are also used in planes to throw out chaff, which distracts approaching aircraft or missiles.
This explosives use led to slang terms like “wet squib,” since a squib which is wet cannot light up, because the moisture soaks the charge and the fuse. Some regions of the world simply refer to any dud firework as a squib.
In the world of Harry Potter, squibs are relatively unusual, and they are sometimes viewed as figures of pity. Because they are born into a magical world, they are aware of their potential, and they may also experience pressure from their families to express magical abilities. Some squibs live at the fringes of the magical world as servants and clerks, while others pursue lives in the muggle community, where they will not be constantly reminded of their failure.