Comic-Book Thud is a sound effect used in comic books to indicate a loud, physical impact. It is usually represented by the onomatopoeia 'BAM' and is often accompanied by an exclamation mark or a starburst. The sound effect is used to emphasize the physicality of a character's action, such as a punch or a kick. It is also used to indicate the sound of an explosion or a crash. Comic-Book Thud is an iconic sound effect that has been used in comics for decades and is still used today.