look up any word, like eiffel tower:
 
5.
A card game where you basically try to beat the dealer by getting as close to a total of 21 as possible without going over. A picture card and an Ace counts as 21, or Blackjack. This is one of the best games to play when you are in a casino given the low winning advantage of the house.
If the tourists spent more time playing Blackjack, Poker, and Craps, and less time playing the slots, the casinos would be making a whole lot less money.
by AYB October 26, 2003
 
1.
A word applied for weed measurements. A blackjack is ¾ oz. (21g).

The word "blackjack" is derived from the popular gambling game, which is often called "21".
- Hey pal, I'd like to buy a blackjack.
- Ight, it'll be 100$.

I smoked that blackjack all by myself!!
by Poulin La-Terreur September 19, 2011
 
2.
a small, light club used for knocking people out
by The Wraith November 05, 2003
 
3.
a fan of the k-pop group 2ne1.

in the card game, blackjack equals 21 which not only is pronounced the same as the group's name, but also signifies a win. therefore, the fans are referred to as blackjacks.
person 1: Do you like 2ne1?

person 2: Hell yeah I'm a total BlackJack!
by omgitsshelbyy December 03, 2010
 
4.
1. Noun: A sex position in which a man defecates on a woman's face whilst performing a "reverse 69."
2. Verb: The act of defecating on a woman's face whilst performing a "reverse 69". In preparation, the man usually drinks a pint of laxative, and then, whilst positioning his penis for insertion into the woman's mouth, instead releases a flood of watery diarrhea into her open mouth and upon her face.
1. Girl, "My boyfriend gave me a blackjack last night."
Friend, "Really? How was it?"
Girl, "Not bad, but I got some corn in my eye."

2. Frat Guy 1, "Hey Bra, remember that time that I totally blackjacked you? That was awesome."
Frat Guy 1, "Yeah Bro! That shit ruled!"
by Captain Hot Pocket October 25, 2008
 
6.
The only game worth playing in a casino. In all the other games, the house has a bigger advantage. Some people use a method called card counting to know when to bet high and when to bet low.
Also, the combination of 2 cards equaling 21 in the game.
Blackjack is also called twenty-one.
by Ed April 05, 2005
 
7.
a weapon used to crack people's skulls open
Ex:Fishing weight on the end of a large spring
I cracked his head open with a black jack.
by The Fonz985 November 05, 2005