Spherical.
Of or relating to the heavenly orbs, or to the sphere or spheres in which, according to ancient astronomy and astrology, they were set.
Helical, like a spiral.
To increase continually.
To cause something to spiral.
To move along the path of a spiral or helix.
A helix.
A section of track that forms a circle and crosses over itself, used for gaining height in mountainous territory.
A self-sustaining process with a lot of momentum involved, so it is difficult to accelerate or stop it at once.
A curve that is the locus of a point that rotates about a fixed point while continuously increasing its distance from that point.