A bar at which drinks are served without charge, usually at a social event.

plural of open market

(finance) The beginning of formal trading on an exchange, usually signalled by the opening bell.

Synonym of free market

(mathematics, logic) An operation on logical values that changes true to false, and false to true.

An expanse of an ocean, sea, or large lake which is distant from shore and devoid of nearby islands or other obstructions.

(idiomatic) To remain vigilant for someone or something. / (idiomatic) To remain vigilant for a possibly dangerous situation.

A showing of something — such as a variable, term, or object — in terms of the specific process or set of validation tests used to determine its presence and quantity.

plural of open sesame

A terminal node in phylogenetic analysis; an organism.