stock ahead

Situation in which two or more orders for a stock at a certain price arrive about the same time, and the exchange's priority rules take effect. N.Y.S.E. Rules stipulate that the bid made first should be executed first or, if two bids came in at once, the bid for the larger number of shares receives priority. The bid that was not executed is then reported back to the broker, who informs the customer that the trade was not completed because there was "stock ahead." See: ahead.