Rat runner is a term used to describe someone who works tirelessly without any concern for their well-being. This term has a negative connotation and is often used to describe someone who gets caught up in the rat race of life. Synonyms for rat runner include workaholic, drudge, toiler, and hustler. A workaholic is someone who is addicted to work and spends all their time and energy on it. A drudge is someone who has a tedious and menial job. A toiler is someone who works hard and doggedly. A hustler is someone who works hard to make a living by any means necessary.