Poinsot's spiral

Poinsot's spiral

[pwän′sōz ¦spī·rəl]
(mathematics)
Either of two plane curves whose equations in polar coordinates (r,θ) are r cosh n θ = a and r sinh n θ = a, where a is a constant and n is an integer.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.