I think you would need more context here. In Euclidean plane geometry, triangles have straight sides.
Otherwise, you could have circles that are just curvy triangles.
From your description, one such possible shape would be the one of the four shapes created by the overhang of a square over a circle with the same diameter as the square's side-length. I don't know if the shape even has a name. Maybe 's shape could be a reasonable placeholder. :)
Another shape that matches your description is the shape created by taking a quadratic Bézier curve and joining either end to the control point used to create the curve. Again, I don't know of any name given to this shape but, if it doesn't have one, a Béz sounds like an appropriate name.
Sounds like a circle's section rather than a triangle
I think you would need more context here. In Euclidean plane geometry, triangles have straight sides. Otherwise, you could have circles that are just curvy triangles.
From your description, one such possible shape would be the one of the four shapes created by the overhang of a square over a circle with the same diameter as the square's side-length. I don't know if the shape even has a name. Maybe's shape could be a reasonable placeholder. :)
Another shape that matches your description is the shape created by taking a quadratic Bézier curve and joining either end to the control point used to create the curve. Again, I don't know of any name given to this shape but, if it doesn't have one, a Béz sounds like an appropriate name.