Real Dictionary

conchoid in American English
a curve traced by an end point of a segment of constant length located on a straight line that rotates about a fixed point, while the other end point moves along a straight line that does not go through the fixed point
noun: a plane curve such that if a straight line is drawn from a certain fixed point, called the pole of the curve, to the curve, the part of the line intersected between the curve and its asymptote is always equal to a fixed distance. Equation r = b ± a sec θ

conchoid in British English
noun: a plane curve consisting of two branches situated about a line to which they are asymptotic, so that a line from a fixed point (the pole) intersecting both branches is of constant length between asymptote and either branch. Equation: ( x – a)2(x2 + y2) =