The term 'Sound of a Slug' can be summarized by two crossword solutions: POW (3 letters) and BAM (3 letters). The sound of a slug is usually associated with the sound of a punch or a hit, which is why the two words are used to describe it. POW is an onomatopoeia that is used to represent the sound of a punch or a hit, while BAM is another onomatopoeia that is used to represent the same sound. Both words are used to describe the sound of a slug, which is usually a loud thud or thump.