In the buff
Definition 1 of 1
Pro Tip 1/3Context Sensitive
This phrase is typically used in informal settings and might not be suitable for formal or professional situations. 
I wouldn't mention him being in the buff at the work meeting.
Pro Tip 2/3Connotation Playful
The phrase often carries a playful tone, suggesting a lighthearted or humorous situation involving nudity. 
They were playing cards in the buff and couldn't stop giggling.
Pro Tip 3/3Privacy Expected
Use it to describe situations where nudity is expected or normal, like changing rooms or private beaches. 
Everyone was in the buff at the secluded lake.