all-or-none

(ôl'ər-nŭn')
adj.
Characterized by either a complete response or by a total lack of response or effect, as in neurological action above a threshold: "Nerve impulses follow the All or None Law-that is, a nerve impulse generated by a weak stimulus is just as strong as one generated by a strong stimulus" (Fundamentals of Biology).

A condition used on a buy or sell order to instruct the broker to fill the order completely or not at all.

Investopedia Says:
For example, if you send a AON order to your broker requesting 200 shares at $15, the broker will not fill the order unless s/he can get you the 200 shares at $15. This prevents you from having orders half filled before they expire.

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Investment banking: an offering giving the issuer the right to cancel the whole issue if the underwriting is not fully subscribed.

Securities: buy or sell order marked to signify that no partial transaction is to be executed. The order will not automatically be canceled, however, if a complete transaction is not executed; to accomplish that, the order entry must be marked Fok, meaning Fill or Kill.