What rhymes with cissoid?
cis·soid

In geometry, a cissoid ((from Ancient Greek κισσοειδής (kissoeidēs) 'ivy-shaped') is a plane curve generated from two given curves C1, C2 and a point O (the pole). Let L be a variable line passing through O and intersecting C1 at P1 and C2 at P2. Let P be the point on L so that O P ¯ = P 1 P 2 ¯ . {\displaystyle {\overline {OP}}={\overline {P_{1}P_{2}}}.} (There are actually two such points but P is chosen so that P is in the same direction from O as P2 is from P1.) Then the locus of such points P is defined to be the cissoid of the curves C1, C2 relative to O. Slightly different but essentially equivalent definitions are used by different authors. For example, P may be defined to be the point so that O P ¯ = O P 1 ¯ + O P 2 ¯ . {\displaystyle {\overline {OP}}={\overline {OP_{1}}}+{\overline {OP_{2}}}.} This is equivalent to the other definition if C1 is replaced by its reflection through O. Or P may be defined as the midpoint of P1 and P2; this produces the curve generated by the previous curve scaled by a factor of 1/2.

more definitions for cissoid »