[ sis-oid ]
/ ˈsɪs ɔɪd /

noun Geometry.

a curve having a cusp at the origin and a point of inflection at infinity. Equation: r = 2a sin(θ)tan(θ).

Origin of cissoid

1650–60; < Greek kissoeidḗs, equivalent to kiss(ós) ivy + -oeidēs -oid

Related forms

cis·soi·dal, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for cissoid


/ (ˈsɪsɔɪd) /


a geometric curve whose two branches meet in a cusp at the origin and are asymptotic to a line parallel to the y -axis. Its equation is y ²(2a – x) =x ³ where 2a is the distance between the y -axis and this line


contained between the concave sides of two intersecting curvesCompare sistroid

Word Origin for cissoid

C17: from Greek kissoeidēs, literally: ivy-shaped, from kissos ivy
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012