To make worse; to make inferior in quality or value; to impair.
To grow worse; to be impaired in quality; to degenerate.
To sell a financial product, such as a share, that one does not presently own, as in the hope of buying it more cheaply later for delivery, so as to profit from a fall in price; cf. go long.
(intransitive, or transitive with of) To have an insufficient amount (of).