noun
A portable lock with a shackle that can be passed through an opening.
自転車に南京錠をかける。
I put a padlock on my bicycle.
南京錠の鍵をなくしてしまった。
I lost the key to the padlock.
The term 南京 (Nanking) was historically used in Japanese to refer to foreign or imported items, similar to how 'Dutch' was used in English. Thus 南京錠 literally means 'Nanking lock', indicating a type of lock introduced from abroad.