Whales are holders and traders of cryptocurrencies that have quantities and capital sufficient to move the market by themselves. Most of these whales are large institutions, but many are wealthy individuals or groups of individuals.

The term derives from the metaphor that the market is the ocean. Whales are so big that other inhabitants have to get out of their way, and the whale can fight any current that resists them.

It's key to note that one could be a whale by holding a large percentage of a currency with a low market cap. Even having $50k in a coin of $1M market cap can be sufficient to manipulate the price.

And a whale can also be a billionaire without holding a lot of crypto. Nothing is stoping Warren Buffet from coming in and purchasing 100,000 BTC, waiting for the market to get euphoric as the price skyrockets, and then selling it all 30 mins later, crashing the price. That scheme is called the "pump and dump."