The Collaborative International Dictionary of English v.0.48:
Federal \Fed"er*al\, a. [L. foedus league, treaty, compact; akin
to fides faith: cf. F. f['e]d['e]ral. see Faith.]
1. Pertaining to a league or treaty; derived from an
agreement or covenant between parties, especially between
nations; constituted by a compact between parties, usually
governments or their representatives.
The Romans compelled them, contrary to all federal
right, . . . to part with Sardinia. --Grew.
(a) Composed of states or districts which retain only a
subordinate and limited sovereignty, as the Union of
the United States, or the Sonderbund of Switzerland.
(b) Consisting or pertaining to such a government; as, the
Federal Constitution; a Federal officer.
(c) Friendly or devoted to such a government; as, the
Federal party. see Federalist.
Federal Congress. See under Congress.