It stands for average daily volume order; an order that aims to trade the average daily volume (ADV) in a security. It involves the average number of securities (e.g., shares) traded over a specific period of time (trading window). The order targets market liquidity available at a certain period of time, as reflected by the average daily volume calculated over the course of a specified window of time (typically 30 days).

It is also known as an ADTV order.