Meaning

noun the leading units moving at the head of an army

noun any creative group active in the innovation and application of new concepts and techniques in a given field (especially in the arts)

noun the position of greatest importance or advancement; the leading position in any movement or field

originEarlier forms included vandgard and (a)vantgard with or without aphetism, derived from Old French avan(t)garde (“before guard”). Doublet of avant-garde and vaward.

Etymology from Wiktionary, CC BY-SA 3.0