flyweight

noun3

1. •
   A weight class in many combat sports; e.g. in professional boxing of a maximum of 112 pounds or 50.8 kilograms.
2. •
   (figurative) Small, light or unimportant.

   • The characters of "Sex and the City 2" are flyweight bubbleheads living in a world which rarely requires three sentences in a row. — 2010
3. •
   A weight that moves outward depending on centrifugal force.