(noun) Substances produced by chemical reactions in living organisms. Types of biochemical compounds include carbohydrates, proteins, lipids, and nucleic acids.

(noun) One who repeatedly uses force or threat to abuse, intimidate, or aggressively dominate others with an imbalance of social or physical power. For many months the fourth grade bully threatened the younger boy by taking his lunch.

(verb) Repeated, aggressive behavior in which there is a real or perceived imbalance of power. Alicia was bullying one of the younger students in her class, calling him names and constantly drawing attention to his insecurities.

(noun) They're witnesses to the bullying or know it is occurring. During school lunchtime, many bystanders watched when a new girl was teased.