In finance, a "long squeeze" describes a situation in which investors who have taken a "long" position feel compelled to sell into a rapidly falling market to prevent even further losses. In a long squeeze, the selling of assets would push down prices even further, exacerbating the squeeze.
In contrast to its more common and much more famous little brother, the "short squeeze", the long squeeze rarely happens in practice in stock or bonds markets. One reason is that when the market price of an asset falls too low, below what most people think it is actually worth, "value buyers" will step in to buy the asset at what they think is a bargain price, driving the market price upward again.
Another reason why long squeezes are rare is that in contrast to investors in a "short" position, who are contractually obligated to provide the promised shares or assets on demand, most investors in a "long" position have no legal obligation to sell, and thus if they feel that the stock has fallen below its true worth, many of them will simply choose to wait it out until prices rise again, rather than being in any way "squeezed" into selling.
The one time that long squeezes are comparatively more common is in futures contracts, because in these contracts both the seller and the buyer have a legal obligation to close out their positions at a certain date, and thus either one may find themselves squeezed by market conditions.