Mongo authentication user can't drop database my question is - is it possible to define user in the Mongo database who will be able to drop the database? Maximum user privilege is "dbAdmin" but that privilege doesn't allow users to drop the database, only collections can be dropped.

I know that "clusterAdmin" has rights to drop the database, but that role can't be defined in regular database, only in admin database...
No, it is not currently possible (in version 2.4) to create such a user/permission.

Permissions on a specific database grant permissions on entities contained in that database, but not on the database itself.  Cluster level permission is needed to create or drop databases.

Reference: http://docs.mongodb.org/manual/reference/user-privileges/#database-administration-roles