plural of open-field test

A scientific test to gauge an animal's locomotor activity levels, anxiety, and willingness to explore, by placing the animal in an enclosed arena and observing its actions.

(uncountable) A genre of opera, often with magical elements. / (countable) An individual opera in this genre.

(uncountable) A genre of opera written to be performed with a chamber ensemble. / (countable) An individual opera in this genre.

operations research

(Of an object) that opens, or is designed to open automatically, or opens of its own accord.

employment contract without a set date for termination

The control mechanism by which a door is latched and unlatched. / Any of various devices to automatically open a door in response to a sensor or signal sent from a controller.

(chess) Synonym of Ruy Lopez

(law) A requisite condition of adverse possession stipulating that the disseisor's occupation of the property must be visible and provide reasonable (if tacit) notice to the disseisee.