Unstable vortex

The unstable vortex, also known as the funnel and nicknamed "kawoosh" by Samantha Carter, is the burst of unstable energy emanating from an activating Stargate.

Description
The vortex is capable of disintegrating virtually anything it touches, including living tissue. The Tok'ra funeral custom has the dead dissolved by an activating Stargate (to dispose of the body with no trace of them ever existing on a particular planet to be found by the Goa'uld).

The Supergate also creates a vortex, but at a much greater intensity because of the much larger amounts of energy transferred into the supergate. Thus far, it is one of the few things known to overwhelm the shields on an Ori battlecruiser.

The Asgard auto-dialer is capable of dialing a Stargate while preventing a vortex from forming. Ascended beings also possess this ability with their mind. The Nox also possess a similar technology to the Asgard.

When Atlantis was infiltrated by Michael, the unstable vortex was used to destroy most of his Puddle Jumper (some of it was out of reach of the vortex). Zelenka lowered Atlantis' Gate shield, allowing McKay to dial the Stargate from another Puddle Jumper outside. With Michael's Jumper parked right in front of the Gate, the unstable wormhole disintegrated most of it.

Behind the scenes
In Stargate Infinity, the vortex does not dissolve whatever it touches.

In the original movie, when the vortex returned to the gate, it inverted into a whirlpool-like form, which Roland Emmerich nicknamed the "strudel". This effect was not transferred into the series.