If you do not care about the data in management database; i.e. users, vhosts, messages etc., and neither about other queues, then you can reset via commandline by running the following commands in order:
WARNING: In addition to the queues, this will also remove any
usersandvhosts, you have configured on your RabbitMQ server; and will delete any persistentmessages
rabbitmqctl stop_app
rabbitmqctl reset
rabbitmqctl start_app
The rabbitmq documentation says that the reset command:
Returns a RabbitMQ node to its virgin state.
Removes the node from any cluster it belongs to, removes all data from
the management database, such as configured users and vhosts, and
deletes all persistent messages.
So, be careful using it.