Meaning relevant or appropriate; refers to the nature of a pending bill’s amendments. In the House, amendments must be germane unless permitted as an exception to the rule. According to Senate rules, amendments need not be germane, except to “general appropriation bills, budget measures, and matters under cloture (and a few other bills, pursuant to statutes)”. (See the Senate Legislative Process) In addition, Senate unanimous consent agreements may require that amendments be germane.
According to Capitol Net: The 1974 budget act also requires that amendments to concurrent budget resolutions be germane. In the House, floor debate must be germane, and the first three hours of debate each day in the Senate must be germane to pending business.
The differing rule requirements can cause conflicts between House and Senate: “conference agreements may include provisions that violate a basic principle of House procedure.” (See Germaneness Rules and Bicameral Relations in the US Congress)