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.
Kirk and Spock also used the suits to escape the tower that shot down their shuttle after planting explosives to blow it up. (TOS video game: Star Trek)