helicline
A curving or spiral-shaped ramp; (especially) the ramp at the 1939 New York World's Fair Theme Center.
uncommon
A bridge will link the sphere to the tower, while from the latter a ramp 900 ft. long will slope gently to the ground curving around the fountain basis beneath the sphere in a huge three-quarter circle. This ramp is described as the “helicline,” and will be 50 ft. high at the top
Where it comes from
Blend of helico- + incline or combination of heli- + -cline, from Ancient Greek ἕλιξ (hélix, “spiral”). Attested from the 1930s (see quotations below).
Adapted from the Wiktionary entry helicline (CC BY-SA 4.0).