limaçon
noun
li·ma·çon ˌlē-mə-ˈsōⁿ 
: a plane curve whose equation in polar coordinates has one of the forms ρ = a cos θ ± b or ρ = a sin θ ± b and which reduces to a cardioid when a = b
Word History
Etymology
French, literally, snail, from Old French, diminutive of limaz slug, snail, from Latin limax; akin to Russian slimak snail and probably to Old English līm birdlime — more at lime
First Known Use
1873, in the meaning defined above