The following descriptions are taken from the game itself.
Compete against your friend in a no-holds barred race to the finish line. Too tame for you? Earn laps in Death Race mode by killing your opponent instead of racing them.
Multiplayer - Single Race
Challenge your opponent to an entire season of races. Choose from four different seasons, each with five races.
Multiplayer - Season
Steal the van, deliver it, and stash the cash. Sounds simple - but your opponent wants the same van and the same cash. Be careful, the more the van is damaged the less cash you get on delivery.
Multiplayer - Stash Dash
Defend The Base
Team up with a friend to defend your base against attack from multiple waves of computer controlled enemies. If the enemy destroys your base's vehicles before the game expires...you lose!
Multiplayer - Defend The Base
Meet up with your friends, then shoot each of them in the face. Similar to the "Liberty City Survivor" mode in GTA Liberty City Stories' multiplayer, and named after the Liberty City Survivor reality show in GTA III.
Multiplayer - LC Survivor
Attack the objectives, or defend them against attacks.
Multiplayer - Gang Bang
There are no online multiplayer options, only weapon trading, drug trading, and the Rockstar Social Club.