Trades that are conducted between two counter parties without using a formal exchange.
While most trading is done on exchanges, some parties may choose to trade over the counter, or OTC, using broker-dealers. OTC trades typically involve large amounts that the parties involved don't intend to broadcast publicly.
In the NFT niche, OTC trades represent NFT transactions done privately, without using marketplaces like Opensea. Such transactions typically have more risk involved, especially in the absence of trusted intermediaries.