A "Sell Wall" is a situation where a large limit order has been placed to sell when a cryptocurrency reaches a certain value.
In the context of cryptocurrency trading, a sell wall is a situation where a large limit order has been placed to sell a certain cryptocurrency when it reaches a certain price. Sell walls are represented visually on a depth chart, creating a "wall" appearance. Traders use the depth chart and the sell wall as visual indications of the respective demand and supply at different price levels. A sell wall can be a manipulative tactic used by traders to create artificial supply bottleneck, stalling the price rise of a cryptocurrency.
For example, if a large number of traders decide to sell Bitcoin once it reaches $10,000, this could create a sell wall at that price level. Until all the sell orders at this price are fulfilled, it would be difficult for Bitcoin to rise above $10,000.