1) In biblical terms, The Flood is essentially an apocalyptic event in which Noah, the only man meant to survive a worldwide deluge, takes 2 of each animal on an ark to avoid the complete and utter distruction of God's creation.

2) The "weapon" in Halo that The Covenant was in desperate search of acquiring in order to wipe out mankind (NOTE the similarity between this and definition 1.) The Flood itself, is actually a humanoid, body-snatching race of fungal origin and consists of 4 subtype species. Can easily be n00bed via shotgun.
"I just learned about The Flood in Sunday School."

"I just n00bed 3 flood with one shotgun blast."
by sux0r October 2, 2003
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a large number of people jumping one person.it is used in chi-town
yo son we flooded his ass after all that mouth he was popin
by miss shyster November 19, 2006
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In Halo 2, Flood are parasites that infect any living organism, taking over their motor functions. The Flood parasite uses the host to reproduce its spores. Since they do not discriminate between various speciaes, the Flood will fight both the humans and the Covenant.
The Flood are one of the most formidable enemies you'll encounter.
by Dan January 21, 2005
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When attending a Halo party and not participating in a round, silently approach the back of whoever appears to be winning the current round and ejaculate all over the back of that player's head.
Player: "I'm ahead b 5 frags... what the hell was that?!?"
Bystander: "The Flood!"
by fagmuffin February 24, 2005
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flood

Background: Middle English, from Old English flOd; akin to Old High German fluot flood, Old English flOwan to flow

1 a : a rising and overflowing of a body of water especially onto normally dry land; also : a condition of overflowing <rivers in flood> b capitalized : a flood described in the Bible as covering the earth in the time of Noah

2 Children who have grown such that the trouser legs are not long enough are pejoratively said to be wearing "floods" (a reference to hiked pants to keep them dry in flood times). This is usually caused by a : suffering from extreme poverty; b : their parents looked down on them with contempt or aversion and therefore weren’t concerned enough to keep them in appropriately fitting clothes.

3 The act of sending numerous Instant Messages, Chat Invitations or Text Messages in a small time frame; whether accidentally or in the hopes of annoying people and crashing their IM program.
Examples:
1. I woke up one morning and the bathroom was flooded with dirty brown water. Apparently Barith had taken a big deuce causing the toilet to rise and overflow onto the normally dry tile of the bathroom floor.

2. None.

3. My phone bill was over $200 last month because Washer Woman kept flooding my phone with trivial things about her mundane life.
by Jendo October 29, 2004
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Usenet: A large number of posts uploaded about the same subject.
Hey did you see the flood of DragonForce MP3s on newsgroups the other day?
by Chris J Pisarczyk June 24, 2005
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The lifeforms in Halo that infect corpses and basically turn them into zombies. Then it turns into Resident Evil in space. The best way to deal with them is with shotguns and energy swords.
"Screw this shit! I'm not paid to star in Resident Evil!"-Master Chief, from the flash, "There's Something About Halo."
by i_anonymous December 7, 2004
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