Ultra vs. Infra — What's the Difference?

Ultra was the designation adopted by British military intelligence in June 1941 for wartime signals intelligence obtained by breaking high-level encrypted enemy radio and teleprinter communications at the Government Code and Cypher School (GC&CS) at Bletchley Park. Ultra eventually became the standard designation among the western Allies for all such intelligence.

(legal) Discussed later.

An extremist

Below; beneath; under; after; - often used as a prefix.

Short for ultramarathon

(in writing) see below;

Immoderately adhering to a belief, fashion, or course of action; extreme.

An extremist.

Extreme; far beyond the norm; fanatical; uncompromising.

An ultraroyalist in France.

An extremist, especially an ultranationalist.

(soccer) An especially devoted football fan, typically associated with the intimidating use of extremist slogans, pyrotechnics and sometimes hooligan violence.

(athletics) An ultramarathon.

(climbing) An ultra-prominent peak.

Code name used by British codebreakers during World War 2 for decrypted information gained from the enemy.

Going beyond others, or beyond due limit; extreme; fanatical; uncompromising; as, an ultra reformer; ultra measures.

One who advocates extreme measures; an ultraist; an extremist; a radical.

(used of opinions and actions) far beyond the norm;