perma-borrow 

To borrow something from someone when you clearly have no intention of returning it or you intend to wait and see if they ever ask for it back.

I perma-borrowed my neighbor's lawn mower 14 months ago and he still hasn't asked for it back.

perma-borrow by College Professor March 23, 2008

permaborrow 

Verb: to borrow, in a permanent manner. To borrow with neither inclination nor intent to return.

Last summer, I permaborrowed my buddy's sweater.

permaborrow by Scaryberry January 21, 2004