Event horizon

Entrance and exit point of an object's journey through the Stargate where matter is disintegrated and then reintegrated.

The event horizon appears to be a bright, iridescent pool of water, standing completely vertical within the ring of an active Stargate.

KEY EPISODES

"Stargate" the Movie - Dr. Jackson admires the event horizon before passing through the Stargate for the first time.
Children of the Gods - Captain Carter admires the event horizon before passing through the Stargate for the first time.
The Enemy Within - Possessed by a Goa'uld, Major Charles Kawalsky is killed when the Stargate is deactivated while his head is in the event horizon.
Shades of Grey - To prevent the Stargate from shutting down so the rogue N.I.D. agents could redial and escape to another planet, Jack O'Neill keeps his arm in the event horizon after traveling through.
48 Hours - To save Teal'c's life, Carter must find a way to create an event horizon without actually establishing a wormhole to another planet.
Air, Part 3 - With the Destiny about to disconnect the gate and enter F.T.L., Dr. Rush tells Eli Wallace to stick his arm into the event horizon to keep the gate open long enough for his friends to make it back.