From the game Call of Duty: Modern Warfare 2 (CoD; MW2), which requires a 11 killstreak in any multiplayer game (10 with hardline) or if your lucky from a care package or emergency airdrop (Both Team or Enemy). It hovers in the air for 40 seconds with 3 different weapons.

105mm - A high radius shell able to kill large amounts of players.
40mm - A smaller shell able to kill lone wandering players.
25mm - Less used but is quite effective if shooting at windows and doors in buildings.

AC130s are quite difficult to shoot down requiring 3 lockon missiles, 2 will miss from its offset flares and a direct hit (Note the AT4-HS will not be able to bring it down but will damage it)

Usually newer layers will scramble around and move in packs thinking the AC130 is harmless while more experienced players will move into buildings or attempt to shoot it down. BEWARE AC130s can shoot down killstreaks.

Originating from Modern Warfare 2, an in-game phrase during online play that the announces to your team that a enemy was lucky enough to score an 11 kill-streak and has earned the chance to unleash destruction at the pulling of a trigger.

Hearing this phrase brings panic and chaos and generally leads to 1 of 3 things happening:

1) Players immediately run for the nearest form of cover (e.g. : buildings, houses, etc).

2) A more senior player will whip out a Javelin or AT-4 and aim it at the AC130 in hopes of bringing the rampage to an end before the pilot racks up a 25 kill streak for a nuke.

or 3) Newer players will stand out in the open and fire their guns at the plane, trying to bring it down. This is usually met by a 105mm round or 40mm round from the airplane above.

Following the announcement of the AC130's arrival, chaos ensues along with the howling entrance of 105mm rounds blasting the map to smithereens.

ENEMY AC130 ABOVE

The act of jizzing on everyone from above and switching to different speeds of nut with a 20mm fast spewing nut up to the 105 howitzer spewing cum launcher