From Longman Dictionary of Contemporary Englishundersideun‧der‧side /ˈʌndəsaɪd $ -ər-/ noun [singular] → the underside (of something)
Examples from the Corpus
underside• Her body was dragged over 70 feet on the front and underside of the car.• And such ways of life still continue, the dark underside of surface prosperity.• A colony of ants on the move from one nest site to another exhibits the Kafkaesque underside of emergent control.• Valadon was a remarkable artist who looked at the underside of life.• The sun was setting in a blaze of pink, casting rosy shadows on the undersides of large, wet-looking clouds.• It swipes the underside of the net.• A strip stuck to the underside of the rule worked beautifully: no more slipping, frustration, or wasted tiles! 