Trash talk is a form of spoken insult usually found in sports events, although it is not exclusive to sports or similarly characterized events. It is often used to intimidate the opposition and/or make them less confident in their ability to win, but it can also be used in a humorous spirit. Trash-talk is often characterized by the use of hyperbole or figurative language, such as "Your team can't run! You run like honey on ice!" Puns and other wordplay are commonly used.

Trash-talk has become a debatable term, especially in North American sports, with the greatest trash talkers being acknowledged for both their trash-talking skills as well as their athletic and mental abilities. For example, Larry Bird is regarded as a prolific trash talker and was known for his athletic ability backing up his trash talk.

In sports, trash talk most commonly comes in the form of insults to an opposing player's playing ability or physical appearance which is ethically not acceptable. The intended effects of trash talk are to create rivalry between the players and increase the psychological pressure of opposing players to perform well or to stop the trash-talker from performing well. Trash talk was most famously used by heavyweight boxing champion Muhammad Ali in the 1960s and 70s.

In 1963, Ali even released a popular full-length record album consisting largely of trash-talk poetry. It was entitled I Am the Greatest!, a phrase that became his signature line. Since then, it has become common for boxers, wrestlers, and many other sports competitors to use trash talk. However, in amateur sports ranks, trash-talking is generally frowned upon as unsportsmanlike conduct (especially in youth leagues). Former UFC Featherweight and Lightweight Champion Conor McGregor is an example of a prominent trash-talker; he is considered to be the greatest trash-talker in MMA history. Former UFC fighter Chael Sonnen is also considered by many to be one of the greatest trash-talkers MMA has ever had. Although the practice of trying to distract opponents with verbal abuse is common to virtually all sports, other sports sometimes have their terminology for verbal abuse: for example, cricket calls it sledging and in ice hockey, it is called chirping.

The quality of performance of players under the pressure of trash talk is debated, but one study found that participants who were subject to a trash talk message exerted more effort in completing their task and perceived their opponent with more incivility and rivalry when compared to participants who were subject to a neutral, irrelevant, or no message at all.

While trash-talking frequently focuses on sporting attributes such as physical ability and athleticism, there is also significant trash-talking off-topic including opponent's sexual behavior and relationships. Zinedine Zidane infamously head-butted Marco Materazzi during the 2006 World Cup Final after Materazzi had leveled a puerile insult about Zidane's sister during a verbal exchange a few moments prior. Trash-talk is more prevalent in contact sports than non-contact sports, and it is also more prevalent between male competitors than female competitors.

Smack talk is a slang term seen in chat channels in chat room, blog, and massively multiplayer online game (MMOG) conversations. The term came about in the early 1990s. It generally refers to the use of threatening or intentionally inflammatory language. Smack talk can also be used with bullying, whether that be face-to-face interaction, or cyber-bullying.

Smack talk is also a slang term used in sports. It refers to inflammatory comments made by a person or team in order to insult, anger, annoy or be boisterous toward their opponents. Although it began as a term used by sports fans and athletes, it has spread to all areas of culture where competition takes place. In the United States, it is synonymous with "trash talk".