Undies
/ˈʌndiz/
Definition 1 of 1
Pro Tip 1/3Slang Term
Undies is an informal slang term mostly used in casual conversation. 
Hey, could you pass me my undies from the laundry basket?
Pro Tip 2/3Not for Formal Use
Avoid 'undies' in formal writing or speeches; it's too casual. 
In a business meeting, one would say 'underwear' instead of 'undies'.
Pro Tip 3/3Colloquial Variety
The use of 'undies' varies by region; be aware of local language preferences. 
In the UK, 'undies' may be more common than in other English-speaking regions.