Definitions of lock up
(UK) somewhere that can be locked up and is typically used for storage (=to keep things in)
The stereos are in the lock up.
a jail, especially a temporary one
The room was used as a makeshift lock up until the police arrived.
a long-term investment that cannot easily be sold or realized
Only invest in a lock up if you are certain that you won't need easy access to your money for the duration of the investment.