(transitive, intransitive) Used other than figuratively or idiomatically: see break, open. / To make a breakthrough on a mystery or problem; to cause a breakthrough to be made.

(clothing) Open at the neck.

(music) A tuning of a guitar or other stringed instrument in which the strings sound a chord when strummed together without being pressed against the fretboard.

plural of re-opening

(UK) A double-deck bus with an open, or partially open, top deck.

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

Used other than figuratively or idiomatically: see open, door. / (idiomatic, intransitive, or transitive with to or for) to allow access or facilitate

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.

(US, education) An unselective and noncompetitive college admissions process, where the only entrance criterion is a high-school diploma or a certificate of attendance or General Educational Development (GED) certificate.

(medicine) A fracture of a bone where one or more bone fragments penetrate the skin, forming an open wound.