SWAT is an acronym for Special Weapons and Tactics, which is a law enforcement unit that specializes in high-risk operations. The term 'swing at a fly' is a metaphor for taking on a difficult task. SWAT teams are often called upon to take on dangerous missions, such as hostage situations or active shooter scenarios, that require specialized training and equipment. Therefore, the term 'swing at a fly' can be interpreted as taking on a difficult mission that requires specialized skills and resources.