Added 9 October 2026 underside /ˈʌndəˌsaɪd/ noun Categories: PlacesRare Words noun ! Definition from WordNet 3.1, Princeton University. Pronunciation from Wiktionary, via Kaikki.org. More about underside at Wordnik → Where our words come from → The lower side of anything. Related Words: undersurfacebottomunderneathbelowhindwingfuseunderwearbellyrearabdomensetbackunderbelly Back to today's word