When something is rigged, it's fully equipped and ready to go. You'll usually find this adjective describing a sailboat or ship with masts and sails.
A fully rigged boat has all the necessary ropes, sails, and masts that it needs to travel on the water. While this nautical adjective is narrowly focused on sailing vessels, you can also use rigged to mean "fraudulent" or "tampered with." If a politician talks about a rigged election, he is not-so-subtly accusing his opponent of conspiring to illegally manipulate the outcome of a vote. This meaning comes from a now-obsolete meaning of rig, "a trick."