avant-garde (n.)

(also avant garde, avantgarde); French, literally "advance guard" (see avant + guard (n.)). Used in English 15c.-18c. in a literal, military sense; borrowed again 1910 as an artistic term for "pioneers or innovators of a particular period." Also used around the same time in a political sense in communist and anarchist publications. As an adjective, by 1925.

The avant-garde générale, avant-garde stratégique, or avant-garde d'armée is a strong force (one, two, or three army corps) pushed out a day's march to the front, immediately behind the cavalry screen. Its mission is, vigorously to engage the enemy wherever he is found, and, by binding him, to ensure liberty of action in time and space for the main army. ["Sadowa," Gen. Henri Bonnal, transl. C.F. Atkinson, 1907]

updated on September 25, 2018

Definitions of avant-garde from WordNet
avant-garde (n.)
any creative group active in the innovation and application of new concepts and techniques in a given field (especially in the arts);
Synonyms: vanguard / van / new wave
avant-garde (adj.)
radically new or original;
an avant-garde theater piece
Synonyms: daring
Etymologies are not definitions. From, not affiliated with etymonline.