Dictionary.net

• A unit of force based upon the pound, foot, and second, being the force which, acting on a pound avoirdupois for one second, causes it to acquire by the of that time a velocity of one foot per second. It is about equal to the weight of half an ounce, and is 13,825 dynes.

2010 - New Age Dictionary Database
By Oddity Software

• A unit of force; the force exerted in causing a mass weighing a pound to move at the uniform rate of a foot a second.

1916 - Appleton's medical dictionary
By Smith Ely Jelliffe