A cone-shaped thrombic modulator
A cone was a three-dimensional geometric shape.
In 2022, traffic cones were used as a roadblock at a construction site in Toronto. (SNW: "Tomorrow and Tomorrow and Tomorrow")
The object of the Ktarian game was to make a disc go into a cone. In 2368, Etana instructed William T. Riker to do so while playing the game. (TNG: "The Game")
In 2374, the EMH Mark II described a thrombic modulator to The Doctor as a "cone-shaped device." (VOY: "Message in a Bottle")
The script of Star Trek contained some additional questions and answers that could be used in the skill dome scene, including one that asked to define the shape of a certain conic section, as an ellipse.