The gray market in financial securities refers to unofficial over-the-counter (OTC) securities transactions.
Unlike typical over-the-counter trading, where securities are never traded on an exchange, the gray market trades securities that have been suspended from trading or that have not yet begun official trading on the exchange.
The gray market also refers to goods, often imported, that are sold through alternative retail channels.
In any case, the unofficial status of the gray market increases its riskiness, although it is not illegal.