shave sth off sth: remove very thin pieces from the surface of something, using a knife or other cutting tool. "I had to shave a few millimetres off the bottom of the door to make it shut."
shave sth off sth: if you shave a small amount off something such as a price or a record, you make the price slightly smaller or the record time slightly shorter. "She shaved half a second off the world record."