An ordinary knot in three dimensions suspended in four dimensions to create a knotted 2-sphere. Suspended knots are not smooth at the poles.
Suspended Knot
See also
Spun Knot, Twist-Spun KnotExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Suspended Knot." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/SuspendedKnot.html