under or below an object or a surface; at a lower place or level; directly beneath; "we could see the original painting underneath"; "a house with a good foundation underneath"
on the lower or downward side; on the underside of; "a chest of drawers all scratched underneath"
high level or degree; the property of being intense
the amount of energy transmitted (as by acoustic or electromagnetic radiation); "he adjusted the intensity of the sound"; "they measured the station's signal strength"