[intransitive, transitive]
(Finance 金融;
Stock Exchange 证券交易(所)) to agree to sell shares, currencies, etc. that you do not yet own, in the hope that their price will fall and you will make a profit by buying them later at a lower price
卖空（股票、货币等）◆You have to be able to borrow shares to short them.
想要卖空便要能借到股票才行。