Wild, irrational, and undisciplined.
Extreme; far beyond the norm; fanatical; uncompromising.
An especially devoted football fan, typically associated with the intimidating use of extremist slogans, pyrotechnics and sometimes hooligan violence.
An ultra-prominent peak.
Code name used by British codebreakers during World War 2 for decrypted information gained from the enemy.
An extremist, especially an ultranationalist.
An ultraroyalist in France.
An ultramarathon.