A lock shaped like an elongated letter D, used to secure an unattended bicycle to railings etc.

present participle of double-lock

Third-person singular simple present indicative form of double-lock

(transitive) To lock with two separate locks or bolts. / (transitive) To lock by two turns of the key.

plural of safety lock

A lock that cannot be picked by ordinary means. / (firearms) A lock with some device for preventing accidental firing of the weapon.

A device, fitted with a lock, that is used to immobilise a bicycle when not in use

plural of seat lock

(railways) The lock of a reversible seat in railroad cars.

simple past tense and past participle of tick a lock