The term 'riot dispersal weapon' refers to a type of weapon used to disperse crowds in the event of a riot. The crossword solution for this term is 'Teargas', which is a chemical agent that causes irritation to the eyes, nose, throat, and lungs, resulting in tears, sneezing, coughing, and difficulty breathing. It is often used by law enforcement to disperse crowds and is considered a non-lethal form of crowd control.