Active resistance to legitimate authority — especially God's. Hebrew marad (to rebel, revolt) and marah (to be contentious, rebellious). Scripture treats rebellion with extraordinary seriousness. 1 Samuel 15:23 equates it with witchcraft: For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry. Rebellion against God is the root of the fall (Gen 3) and of Satan's prior rebellion (Isa 14:12-15; Ezek 28:12-17); the NT calls Christians out of children of disobedience (Eph 2:2) into the obedience of faith (Rom 1:5). Rebellion against legitimate human authority is also forbidden (Rom 13:1-5; 1 Pet 2:13-17; Heb 13:17) — submission to magistrates, elders, husbands, parents, employers, each in their God-appointed sphere. The exception is when human authority commands what God forbids: we ought to obey God rather than men (Acts 5:29). Outside that exception, rebellion is sin and is gravely weighted in Scripture.