A long squeeze is when shareholders feel the pressure of falling prices and themselves sell, causing the price to fall even further.

Investors encounter long squeezes fairly rarely, and it usually occurs in more illiquid stocks where a panicked investor will fear riding a stock all the way down, and not finding a buyer at a desired price.

On the contrary, long squeezes are more rare in high volume, larger cap names because opportunistic investors will tend to enter names when prices are falling, as a form of bargain hunting.

What is a Short Squeeze?
What is a Bear Squeeze?