Not Held Order (NH)
Definition - What does Not Held Order (NH) mean?
Not held order is an order that gives the floor broker discretion as to the time and price of execution.
Testopedia explains Not Held Order (NH)
A investor usually a large or sophisticated investor who wants to purchase or sell a block of stock may at time give the floor broker the authority to determine the time and price at which the order is executed. A not held order as the name indicates states that the floor broker will not be held responsible if the order could have been filled at a better price later in the trading session.