Toxic order flow

Market makers and HFTs refer to incoming orders as toxic order flow when it results in adverse selection due to providing liquidity at a loss to an informed trader (metaorder of big institution) or mass-retail buying of stocks or call options induced by viral social media posts or trading chat rooms.

HFTs estimate flow toxicity based on volume imbalance and trade intensity using metrics such as Volume Synchronized Probability of Informed Trading (VPIN).

Reference: David Easley & Marcos M. López de Prado & Maureen O’Hara, 2012. “Flow Toxicity and Liquidity in a High-frequency World,” Review of Financial Studies, Society for Financial Studies, vol. 25(5), pages 1457-1493.