Corner
(FINANCE) Used either as a noun: a situation in which a trader controls the supply of a traded item, such as shares of stock, supplies of a commodity, etc.

Or else, used as a verb: to obtain control over the supply of a thing, so that one can drive the price up to extremely high levels.

Cornering the market for anything (or getting a corner) is extremely difficult and requires not only immense amounts of money (usually borrowed for the purpose), but also timing and the ability to bluff opponents.

A corner is ultimately a long position in the sense that it is a direct attack on investors taking a short position.
The corner must be timed very precisely, because it cannot last for more than a very short time. Even when the the price of the thing (like, say, silver) goes up to very, very high levels, more supplies cannot come onto the market or the corner will be lost.

At the same time, there has to be a target of the corner--some group of people who have to buy the cornered item no matter how high the price goes (otherwise, the quantity demanded will just go to zero). For this reason, corners are nearly always part of an attempt to squeeze the shorts.