Maybe something like “a cryptographic address to find people or services”. It’s a common way to address/identify people or services in the nostr way. 

 Haha that’s more over complicated for none technical people than public key. 
Someone just mentioned “user ID” seems like that might be it 

 Maybe depends a bit on the specifics of who you’re describing NPUBs too and how deep their understanding already goes on this kinda stuff 

 For example here is the reason why I brought it up. 

nostr:note17mt43kckffjafervd0rupf87rgjks2vq5xs00a858z35d9e97mkqq6n999 

 I tried out some additional language to see if it helps at all:

nostr:note17grgk5xmcs9v9ygwmxknuyhj7xr6kngu8cls9e50hr06uamaefhsy5ymjc