The potential a man has to satisfy you. Usually measured in inches of cock (to fill you with).
Joe had the best fill power I had ever seen.
by -= Hannah =- May 12, 2005
1 more definition
The amount of cubic inches one ounce of down occupies. The warmer the down, and the greater the fill power, the more space it will occupy. A fill power of 700 indicates that one ounce of down feathers will occupy at least 700 cubic inches.
by michael November 11, 2003