The S.F.M. was a paramilitary organization before the Cylon Attack who, depending on one's point of view, were freedom fighters or terrorists devoted to overthrowing the tyrannical local government on Sagittaron that was installed by the Government of the Twelve Colonies to facilitate what some believed was an exploitation of Sagittaron's resources by the other Colonies.
Infamous prisoner-of-conscience Tom Zarek was a prominent member of the movement, if not the leader. The group believed in using violence to achieve their goal of freedom, including many acts of terrorism (Bastille Day).
The acronym has not been defined within an episode or official source.