Definition from Wiktionary, the free dictionary
underside (plural undersides)
- The side that is below or underneath, the bottom.
2016 January 23, Michael Emons, “Crystal Palace 1–3 Tottenham”, in (Please provide the title of the work), BBC Sport:
- The Eagles then hit the woodwork twice in a matter of seconds as Scott Dann headed Jason Puncheon's free-kick against the underside of the bar, before substitute Mile Jedinak also hit the crossbar with a shot on the turn.