Weak Longs

What Does Weak Longs Mean?
Refers to the group of investors that holds a long position and is quick to exit that position at the first sign of weakness. This group of investors is generally looking to capture the potential upside in a given security, but is not willing to take much loss. These investors will quickly close their positions when a trade does not work in their favor.

Investopedia explains Weak Longs
Weak longs are regarded as the opposite of true long-term investors because they are not willing to hold their positions through all types of fluctuations. Weak longs are generally short-term traders who are looking for a quick profit. When the situation is not looking good, they will close their positions and go looking for opportunities elsewhere.