(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.

(UK) A system of bus operation where passengers may enter through various doors along the vehicle's length without having to pass the driver to buy or show a ticket.

simple past tense and past participle of open up

plural of open-topper

Having an open top. / (of a vehicle) Having no roof, or having a top folded or detached.

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

(military) A military unit formed up so as to allow space between its ranks. / (nautical) A naval formation in which ships are four cables'-length (2880 feet) apart.

(mechanics) A type of differential gear used in automobile construction, allowing for output shafts to have different angular velocity, while equalizing torque applied to each output shaft.

(Australia) Freedom to act without repercussions; free rein.

(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.