Slug

The imperial unit of mass, defined as that which one pound of force accelerates at one foot per second squared.

The slug is the poundal’s counterpart, approaching the same problem from the opposite direction: where the poundal fixes mass and derives force, the slug fixes force and derives mass. Its value of roughly 32.17 pounds is not arbitrary but exactly the figure required to make the arithmetic of Newton’s second law come out cleanly in feet and seconds. The name appears to have been coined in the early twentieth century, and the unit survives in some American aerospace and ballistics work, having been more thoroughly abandoned in Britain than the poundal ever was.