1.NounAny of a family of curves defined as the locus of a point, P, on a line from a given fixed point and intersecting two given curves, C1 and C2, where the distance along the line from C1 to P remains constant and equal to the distance from P to C2.
"The cissoid of a circle and a line is a conchoid"
2.NounAlternative form of cisoid (“4chan slang, derogatory: cisgender person”).
"(The addition of quotations indicative of this usage is being sought:)"