It stands for all-or-nothing offering; the offering of a security on the condition that its entire issue is sold. If not, the offering is cancelled by the lead underwriter. Most best effort deals are carried out on all-or-none basis whereby a company determines the amount of money it needs to raise and the number of securities that would be enough to secure this amount. If it fails to raise that much, the offering would be cancelled.

Under this type of offering, the would-be-issuing company cannot break escrow until the entire amount of securities is sold and the required money is raised.