A more thorough explanation:

Definition: A lockup is a place where people are held in custody, usually as a form of punishment for breaking the law. It can also refer to a financial option that allows an investor to lock in a specific price for a security.

• After being arrested for theft, the suspect was taken to the local lockup.
• The city council approved the construction of a new lockup facility to address overcrowding in the current jail.
• Investors can use a lockup option to protect themselves from market fluctuations by locking in a specific price for a security.

The first two examples illustrate the use of lockup as a jail or detention facility. The third example shows how lockup can also refer to a financial option used by investors.