A dart was a hand-held weapon. As a projectile, these were propelled by hand, slingshot or blowgun.
In 2268, the USS Enterprise crew attempted to use darts launched by slingshots to subdue Wyatt Earp and his associates. (TOS episode: "Spectre of the Gun", TOS novelization: The Last Gunfight)
On Stardate 14093.4 a Cardassian agent Warad attempted to gain access to the Legaran Ambassador quarters on the Vulcan Space Central space station. Warad used a series of toxin tipped darts fired from a blowgun to incapacitate the guards. (TOS comic: "Enter the Wolves")
Darts was also a popular game.
In 2372, Krozh and another Nausicaan relaxed by throwing darts at each other. (DS9 episode: "Bar Association")