A cudgel is a thick club or stick, used to attack or defend against an attacker. A rioting mob might be armed with cudgels.
A cudgel is a rough kind of weapon — the club a police officer carries, for example, is more likely to be called a baton or a truncheon. An angry protester might wield a cudgel, or a burglar might carry one along during a robbery. The Old English root of cudgel is cycgel, "club with a rounded head," possibly from the Proto-Indo-European geu, "to curve or to bend."