The word "undesirable" refers to something or someone that is not wanted, desired or considered unfavorable. It can be used in a variety of contexts such as describing an action, person, situation or thing that is unwanted or unpleasant. For example, behaviors like lying, cheating and stealing are often seen as undesirable traits in people while pollution, poverty and crime may be considered undesirable conditions in society. In essence, the word "undesirable" conveys a sense of rejection or disapproval.