It stands for midpoint extended life order; an order (a non-display midpoint orders) that only executes against other same type orders (midpoint extended life orders), but different side of the market, following a very short resting period (in milliseconds, e.g., 10 milliseconds). The embedded mechanism helps protect market participants from rapid market movements and adverse selection. In other words, the order allows investors to limit market impact to its minimum, while being able to execute at the best level possible (particularly, long-term investors).

By nature, this order is less aggressive than midpoint orders and CMO orders.