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1.
Someone who is instructed to keep a watchful eye for popo and intruders, while someone or a group engages in illicit activity. Whenever a lookout spots popo or intruders they are required to warn others verbally or physically. Lookouts will typically engage in ordinary behavoir, such as pretending to talk on a cell phone or smoke a cigarette to appear to be occupied and allow them to be watchful at the same time.

There may also be another lookout from a distance watching the main lookout in the case that body gesture or hand movements are used as a warning. This method is preferred in a noisy environment where a verbal signal may not be picked up.
Jon, were gonna case this joint, you be the lookout while we take care of business
by BMoney January 28, 2005
 
2.
<phrase> Warning;

A phrase intending to make another person or group of people aware of a sudden danger which they may not be aware of themselves yet.
ARMY CAPTAIN: "Look out!"
<mortar shell takes out entire squad>
ARMY CAPTAIN: "Shit."
by Stuart Fletcher January 07, 2005
 
3.
Made famous by the late Ronnie James Dio of Rainbow, Black Sabbath, Heaven and Hell and Dio. Dio would often shout at the top of his lungs in parts of a song "Look out!". Best used in context with a loud raspy voice while flashing the horns. Most commonly heard when describing an impending situation or event loosely connected to Heavy Metal.
"Look out" is also a phrase used in tribute to Dio, often yelled by rockers before they down a shot, take a drink or on hearing the opening riff of a Dio song.
*shot glasses poised - "Look out!" - shot drank.

*Black Sabbath's 'Mob rules' opening riff starts - "Look out!"

"Here comes that hot metal chick again, LOOK OUT!"
by Rahtedpumpclart February 27, 2012
 
4.
a vert certain "Cult" call only reconised by the leet community that is of The parramatta region.

It can be called for a number of reason, Although the main reason of the call is to aware local fellow l33tst3rs about the appochen Bogey AKA Bogan in the area.
Joel - Ahh damn tiiight kicks

Justin - Yea, sweet Jordan melo shirt yo'

*bogan enters*

Both - LOOOOKOUTTT

Bogan - EH THA FUCK WHEREZ DA RSLZ OR DA SERVO?

Both - Kthxbai
by justin December 25, 2004
 
5.
When a Bogan enters the room, you better lookout.

Applies to Mr brown, and/or Ramsays dad, JEFF

See MR. Brown, Jeff, Kez
Me - "yo sup joel"
Joel - "nadda mang"
**MR brown enters**
Both - "LOOKOUT"
by justin December 24, 2004
 
6.
An of age person who purchases alcohol for minors.
Although I never would have spoken to him otherwise, I befriended Jeremy because he was 21 and always willing to be my look-out.
by lmg December 14, 2003