cissoid

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From Ancient Greek κισσός (kissós, “ivy”) + εἶδος (eîdos, “form, image”).

cissoid (plural cissoids)

1. (geometry) Any 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

• cissoidal

From cis +‎ -oid.

cissoid (plural cissoids)

1. (4chan /lgbt/ slang, derogatory) A cisgender person.
   • 2025 August 29, anonymous author, “bi trans men in the sense of strictly t4t?”, in 4chan‎^[1], /lgbt/:

     I feel very similar, I don’t ever see myself with a cissoid and I think there is something beautiful about t4t, and every day I am st4t is this truth reinforced. And I always love fellow bisexuals :}

   (The addition of quotations indicative of this usage is being sought:)

• cisoids