From Longman Dictionary of Contemporary Englishthe underside (of something)the underside (of something)BOTTOMthe bottom side or surface of something The leaves are green on top and silvery on the underside. → underside
Examples from the Corpus
the underside (of something)• Take up every fourth or fifth board, so that you can reach between the joists and the undersides of boards.• Turn the frond over and look at the underside.• Valadon was a remarkable artist who looked at the underside of life.• Oil a recent visit, I checked the undersides of the branches of five-hundred-year-old hemlock trees hanging across a creek.• Stripboard component layout and details of breaks required in the underside copper strips.• This ensures that much of the direct sunlight falls on the underside, where the most heat-resistant surfaces are placed.• The concave sole on the underside of the hoof is sensitive and not as hard as the outer wall.• The diary was attached to the underside with sellotape. 