An acrostic is a type of word puzzle in which the first letter of each line spells out a message or word vertically. Synonyms for the word "acrostic" are word game, puzzle, riddle, quiz, and enigma. Word games are often used as a way to exercise the mind and improve cognitive function. Puzzles can be challenging, but also fun and rewarding when solved. Riddles have been used for centuries in storytelling, as well as for amusement and intellectual stimulation. Quizzes are typically used as a way to test knowledge or assess proficiency in a particular subject. Enigmas, a more general term, refers to any type of puzzle or mystery that requires deep thought or investigation to solve.