The term 'Successful Turn in Battleship' can be summarized as a successful attempt to HIT an enemy's ship in the game of Battleship. The three letter solution for this term is 'HIT'. Battleship is a two-player guessing game where each player has a board with hidden ships and they take turns trying to guess the location of the other player's ships. If a player guesses correctly, they have successfully 'HIT' the other player's ship.