The act of purchasing an item that you intend to use and then return for a refund. Technically you "own" the item until it's returned, but you never really intended to pay for it - just borrow, or "borrown" it.
Usually perpetrated by the kind of people who arrange for a 2 day test drive of a 4x4 they have no intention of buying so they don't have to pay for an offroading experience, and then proceed to drive like an asshat through the local trails.
Similar to the term "wardrobing", but "borrowning" can refer to anything returnable, not just clothes.
"Dude, how can you afford a Bang & Olufsen sound system??? Did you borrown it just for the party?"
"Of course she's wearing new Jimmy Choos - she's borrowning them, like all of her outfits! She's like a hobo supermodel. She's a wardrobing queen."