Originally Posted by ChattanoogaPhil

Do you mean a round that fails to fire?

A "squib" refers to a bullet that becomes lodged in the barrel, usually caused by insufficient powder charge. Typically happens with individuals who reload their own centerfire ammo and they simply skip a powder charge. The primer alone can build enough pressure to discharge the bullet into the barrel where is becomes stuck. It's not all that common, but it happens. However, to have a few factory .22lr squibs per box would be the equivalent of winning the lottery a few times a week.