quandle

Coined by David Joyce in his 1982 paper A classifying invariant of knots: the knot quandle.

quandle (plural quandles)

1. (mathematics) A rack, ${\displaystyle \scriptstyle \mathrm {Q} \,}$, such that ${\displaystyle \scriptstyle \forall a\;\in \;\mathrm {Q} }$ ${\displaystyle a\triangleright a=a}$ or equivalently ${\displaystyle a\triangleleft a=a}$.