WordNet
sell short
v. sell securities or commodities or foreign currency that is not actually owned by the seller, who hopes to cover (buy back) the sold items at a lower price and thus to earn a profit
underestimate the real value or ability of; "Don't sell your students short--they are just shy and don't show off their knowledge"
Usage examples of "sell short".
You could sell short and start rumours that the Leader Reef had pinched out at depth.
Long distance is on the wire demanding to know if they should sell short or long.
You can lose your whole stock if you sell short cloth without marking it by cutting the selvage.