adj. Of a type of irregular fracture having planar, concentric curves, like those on a mussel shell. Of a mineral having such a fracture, such as flint.
the GNU version of the Collaborative International Dictionary of English
adj. Having elevations or depressions in form like one half of a bivalve shell; -- applied principally to a surface produced by fracture.
The Century Dictionary and Cyclopedia
In mineralogy, having convex elevations and concave depressions like shells: applied principally to such a surface produced by fracture, as exemplified in obsidian.
In mathematics, pertaining or relating to the conchoid: as, Holm's conchoidal screw.
Word Usage
"This is referred to as conchoidal fracture; glass fractures in the same way."