The term 'sad sack' is a slang term used to describe someone who is a failure or a LOSER. It can be broken down into five different words: moper (5 letters), HANGDOG (7 letters), SCHMO (5 letters), LOSER (5 letters), and yoyo (4 letters). Moper is an informal word for someone who is always feeling down or depressed. HANGDOG is an adjective used to describe someone who looks ashamed or embarrassed. SCHMO is a slang term for someone who is foolish or inept. LOSER is a term used to describe someone who has failed or been defeated. Finally, yoyo is a term used to describe someone who is unpredictable or inconsistent. All of these words together can be used to describe someone who is a sad sack.