What does Freedom Sleeve mean?

A type of sleeve construction used on vintage and reproduction sweatshirts, designed to allow improved movement and ‘freedom’ for the arms and shoulders.

Heddels explains Freedom Sleeve 

A freedom sleeve is set into the body in a way that provides more slack than the normal ‘set in’ sleeve construction. The freedom sleeve is constructed with ‘S’ shaped shoulder seams that allows more room in the underarm, and the arm part of the sweatshirt to run right up to the neckline.

Examples of a Freedom Sleeve

The freedom sleeve of a Cushman sweatshirt via Clutch Cafe