plural of can-opener

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

plural of open market

Synonym of free market

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

plural of open sesame

A straight razor.

plural of open razor

(topology) Informally, a set such that the target point of a movement by a small amount in any direction from any point in the set is still in the set; exemplified by a full circle without its boundary.

partially open; ajar / (mathematics) (referring to an interval on the real line) containing only one of its endpoints