Frangible

A certain learned and curious Author gives us the following Characters or Properties of Glaſs, whereby it is diſtinguiſh'd from all other Bodies, viz. […] That it is frangible when thin, without annealing.

Source: wiktionary

Another object still [of roasting iron ore], is to make the ore more frangible, that it may be easily broken into fragments of a suitable size for smelting.

Source: wiktionary

Folklorists claim that the superstitious belief that opening an umbrella indoors augurs misfortune has a more recent and utilitarian origin. In eighteenth-century London, when metal-spoked waterproof umbrellas began to become a common rainy-day sight, their stiff, clumsy spring mechanism made them veritable hazards to open indoors. A rigidly spoked umbrella, opening suddely in a small room, could seriously injure an adult or a child, or shatter a frangible object.

Source: wiktionary

So, to make sure that I stay both current and deadly, I built the range, where the guys can sharpen their lethal talents, and—careful always to use only approved military weapons—I can sharpen mine. Shooting, after all, is a frangible skill. At SEAL Team Six we shot daily.

Source: wiktionary