triple point

noun

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