The term 'HALF OF A BLACKJACK' can be solved by the word 'ACE', which is a 3 letter word. An ACE is a playing card in a deck of cards, and it is the highest ranking card in most card games. In the game of Blackjack, an ACE is worth either 1 or 11 points, depending on what is most beneficial to the player. Therefore, half of a blackjack would be an ACE, since it is worth half of the total points needed to make a blackjack.