a. [f. as prec. + -AL.]
1. Geom. Pertaining to, or resembling, a conchoid.
1666. Collins, in Rigaud, Corr. Sci. Men (1841), II. 469. Let there be points made in a curve, which will be conchoidal or asymptotic.
1879. G. Salmon, Higher Plane Curves, v. 172. The serpentine is exchanged for the conchoidal form.
2. Min., etc. Applied to a fracture presenting smooth shell-like convexities and concavities.
1802. Playfair, Illustr. Hutton. Th., 287. Their fracture was conchoidal and but slightly uneven.
1865. Lubbock, Preh. Times, iv. (1869), 78. A splintery conchoidal fracture almost as sharp as that of flint.
