The word "rig" can be used to name a thing or describe an activity. Recently, this word has been used as an adjective and as a verb by U.S. presidential candidate Donald Trump. In this case, to rig something is to create a situation that gives an unfair advantage to a person or a group.
The past participle can be used as an adjective:
Trump says that the election is rigged.
He says that the government is rigging the election.
He believes that the media are part of a rigged system.
Rigged elections are not uncommon in some countries. (not uncommon = something regularly happens)
Experts on the U.S. election system say that claims of a rigged election are false.
There are other things that people commonly believe to be rigged.
Some economists say that the stock market is rigged.
Some politicians say the economic system is rigged because it favors the rich while it punishes the poor.
Under a rigged economic system, the rich have figured out how not to pay taxes.
The word "rig" can be used when something is fixed for some purpose:
The man’s car is rigged with lights and a very loud stereo.
We rigged our boat so that it’s easier to use when fishing.
Someone rigged the door so that it would open by sliding into a pocket in the wall.
The word "rig" is also a noun:
Fishing rigs are used by professional fishermen to catch fish.
A large truck might be referred to as a rig.
A trucker drives a big rig.
Machines and computers might be referred to as rigs.
Construction sites may have one or more rigs for digging down into the earth.
An oil rig drills deep down into the ground in order to extract oil.