conchoid

Meanings

1. Any of a family of curves defined as the locus of points p, such that each p is on a line that passes through a given fixed point P and intersects a given curve, C, and the distance from p to the point of intersection with C is a specified constant (note that for nontrivial cases two such points p satisfy the criteria, and the resultant curve has two parts).
2. A conchoidal fracture in rock.

Etymology

From Latin concha (“mussel”) (from Ancient Greek κόγχη (kónkhē)) + -oid or directly from Ancient Greek κογχοειδής (konkhoeidḗs), referring to the curved outline of a mussel shell or anything in this form. By surface analysis, conch + -oid.