A wingsuit was an aerodynamic article of clothing worn over one's clothes for the purpose of flight. An individual utilized it by running towards the edge of a platform or natural outcropping and jumping, spreading their arms out wide. Flaps opened underneath the arms and between the legs of the wearer, causing a glider-like effect. The wearer could maneuver to dodge obstacles and weapon fire midflight.
James T. Kirk and Spock used wingsuits to leave the mountain top in pursuit of T'Mar. Kirk initially agreed to let Leonard McCoy come along on the jump after the latter asked him. One look at the view down below, however, and he declined in favor of remaining in the shuttle and working on the antidote to the Gorn virus, much to Kirk's amusement and relief.
In 2269, Hikaru Sulu and Pavel Chekov wore wingsuits while exploring the Fiilestii's low-gravity habitat module in the Web of Worlds within the atmosphere of the planet Cherela. Sulu found it much easier to glide in the dense air than Chekov, who flew awkwardly at first. (TOS novel: The Face of the Unknown)