Rushing is the term used for a method used by older players which consists of simply getting weapons as soon as possible and then attacking other teams while they are un-armed and vulnerable. Rushing is often frowned upon my most lower-level players and is utilized mainly by players which are high on the global leader board.
Common rushing techniques
One may rush with a Hover Barge by placing Turrets on the bottom, then flying over to an enemy island and placing the Barge over the Spawn so the players are getting spawnkilled, and then destroying the pipe leading to the Spawn Point.
Another method is to arm yourself with the Rocket Launcher, build a Bridge to the mainland and then stand simply bombard the island with your Rocket Launcher. One can then extend this technique by upgrading their jetpack power, jumping onto the island, and then killing the players as well as their Spawn Point by drawing Iridium from the player's tanks.
The last common technique is to quickly fill up a Barge, create a Laser Drill and then hover down to an enemy's supports. Most teams will not have a Spatial Anchor early-game and will most likely not have time to build one, letting you doom their whole island.
One great tip is stated in the game tips: Arm yourself as soon as possible. If you opponent already has a Rocket Launcher and an Assault Rifle, so can you. Build a Turret or two to protect your base. Make a Spatial Anchor ASAP. Hide behind a Spawn Point and use a Rocket Launcher to counter rush Barges. Warn other teams to prepare themselves if you know a certain team will rush somebody.
Worth noting is the Starter Turret, a powerful, but temporary, defensive item designed to counter rushers.