un ‧ der ‧ wear /ˈʌndəweə $ -dərwer/ BrE AmE noun [uncountable]
[ Word Family: noun : ↑ wear , ↑ underwear , ↑ wearer ; adjective : ↑ wearing , ↑ worn ; verb : ↑ wear ]
clothes that you wear next to your body under your other clothes:
You just need to take a change of underwear.