Way to shutdown/freeze/stop an individual database without taking postmaster down?

Greetings,

I was asked this question, and I wasn't sure if it is possible:

do you know of a way to stop just one database (not delete/drop) on
our PostgreSQL 8.1 server?

And, while I know how to shut down postmaster, and/or put in rules to
pg_hba.conf to limit access to a certain database, is there any way to
freeze or stop just one database and not others? I'm attempting to
RTFM it, but so far I've had no luck.

Thanks,
Will