Chine refers to the intersections (or joins) between the sides of the hull of a boat and the bottom of the hull.
A boat with a backbone is termed "single-chine". One with a join on each side, typically a flat bottomed boat, has a "hard-chine". Finally, one with multiple joins as in a typical wooden hulled boat has a "soft-chine".
Chine also refers to the aerodynamic surfaces along the fuselage of the Lockheed SR-71 Blackbird. Chines generate lift-providing vortices and reduce the lateral radar signature of the aircraft.