1.NounThe visible underside of an arch, balcony, beam, cornice, staircase, vault or any other architectural element.
2.NounThe top point of the inside open section of a pipe or box conduit.
"The elevation of the pipe soffit is 10.4 meters above mean sea level.; The vents on the bottom of the soffit should be open, and the vents on the side of the soffit should be closed."