If you criticize or form opinions of others without knowing enough about them, you are being judgmental. Inaccurate judgment is a form of bias and can be damaging to a judged individual's self-concept. It may also be destructive to how others view the person being judged.
Being judgmental refers to the tendency to form an opinion or conclusion about something too quickly and critically. These assumptions can be based on a person’s behavior, morals, actions or beliefs and typically do not take into consideration specific elements of what is being judged For example, you may assume a shy woman is stuck-up or self-centered if she does not engage in conversation with you. Forming a negative opinion such as this without knowing all the facts would be considered judgmental, according to clinical psychologist Gregg Henriques in the Psychology Today article "On Making Judgments and Being Judgmental."