When a two people are arguing back and forth in a public area in a whispering tone. Since it would rude and embarrassing to let the world know what their arguing about, they whisper. Like at huge events or places of business.
*In a whisper tone at a friends wedding*
Nathan: "I know I forgot to get the peanut butter! Let it go already!"
Claire: "No, I'm not letting it go! I specifically told you which kind and where! Multiple times!
Nathan: "You know I'm forgetful! And it doesn't matter right! Just stop, I don't wanna have a whisper war with you right!"