triple point

The unique temperature and pressure at which the solid, liquid and gas phases of a substance are all in equilibrium.
A point where the incident shock wave, the reflected shock wave, the Mach stem, and one slipstream meet.
A point where a curve or surface intersects itself along three arcs.
The intersection of an occluded front, cold front, and warm front.
The point where two boundaries, such as a dry line, outflow boundary, or cold front, intersect.
A point where three plates intersect.