Extreme

Uses for the term extreme, which is sometimes spelled xtreme, include:

Geography and astronomy
 Extremes on Earth
 List of extrasolar planet extremes

Mathematics
Extreme value, the largest or smallest element of a set

Science and technology
Science
Extreme weather, severe or unseasonal weather
Extremism, ideas or actions beyond what is deemed acceptable
Extremophile, an organism which thrives in or requires "extreme" 

Technology
Extreme Networks, a California-based networking hardware company
Extreme Programming, a software engineering methodology
Xtreme Mod, a peer-to-peer file sharing software for Windows based on eMule

Sports and entertainment
Sports
Extreme sport, a sport featuring speed, height, danger or spectacular stunts
Extreme skiing
Extreme Sports Channel, a Netherlands television channel
Extreme Championship Wrestling, a former wrestling promotion
Xtreme Pro Wrestling
Los Angeles Xtreme, a defunct XFL franchise
Xtreme Turf, an artificial turf or synthetic grass system

Music
Extreme (band), an American band
Extreme (album), an album by Extreme
Xtreme (group), a bachata duo
Xtreme (album), an album by Xtreme
Extremes (album), an album by Collin Raye
Extreme Records, a record label
Agostino Carollo or X-Treme, an Italian singer, DJ, and producer

Entertainment
Extreme (CSI: Miami)
Extreme (TV series)
Going to Extremes, a UK television series
Extreme (Travel Channel series), a US television series
Extreme Associates, an adult film production company
Dance Dance Revolution Extreme, a music video game by Konami
Extreme Paintbrawl, a first-person shooter video game
Dance Dance Revolution Extreme (North America), a music video game by Konami

Games
Extremes (Combat Arms)

Literature
Extreme Studios, a defunct studio of Image Comics
Adam X the X-Treme, a Marvel Comics character
Extreme, an autobiography by Sharon Osbourne

Other uses
Extreme Pita, a Canadian-based restaurant chain
Chevrolet S-10 xtreme