a common scrubby deciduous tree of central and southeastern United States having dark bark and broad three-lobed (club-shaped) leaves; tends to form dense thickets
"After clearing the dense thicket of blackjack trees from our property line, we finally had room to plant flowers."
a flag usually bearing a white skull and crossbones on a black background; indicates a pirate ship
"The lookout spotted a menacing vessel flying a stark black flag emblazoned with a white skull and crossbones as it approached the harbor."
a gambling game using cards; the object is to hold cards having a higher count than those dealt to the banker up to but not exceeding 21
"He placed his last chip on the table, hoping his final card would make blackjack and beat the dealer."
A common gambling card game in casinos, where the object is to get as close to 21 without going over.
"After watching their comeback stage for hours, I finally admitted to my friends that I am an official blackjack."
A fan of the South Korean girl group 2NE1.
In plain English: Blackjack is a popular card game where players try to get a hand totaling twenty-one to beat the dealer.
"He won the game when he was dealt an ace and a king for blackjack."
Usage: The term "blackjack" refers to a card game or a blunt weapon, not a fan of the South Korean group 2NE1. Fans of that group are called 2N1s or Blackjacks only within their specific fandom context, which is not the word's standard everyday meaning.
To strike with a blackjack or similar weapon.
"The guard tried to stop him, but he managed to escape after striking the man in the face with a blackjack."
In plain English: To blackjack someone means to push them down hard enough that they fall over.
"He decided to blackjack the suspect into confessing while the room was empty."
Usage: Do not use "blackjack" as a verb to mean hitting someone; that action should simply be described as beating or striking them. The term "blackjack" refers only to the specific blunt weapon used in such an attack, not the act itself.
The word blackjack is simply a combination of the words black and jack. It was first used to describe a specific card game played with a single deck where players bet on whether the dealer would have a "blackjack" hand.