Picture a column of people on the move, and one small group riding well out in front of it. They are the first to see what is ahead, and from behind they look odd, because they are already somewhere the rest of the column has not reached. Every use of avant-garde keeps that shape: something or someone is out in front, and the strangeness others feel is just the distance between them.
From Old French avant (before, in front) + garde (guard) — the troop riding at the very front of an army. English vanguard comes from the same source.
來自古法文 avant（在前面）＋ garde（衛隊），原本指軍隊最前頭的那一支先遣部隊。英文的 vanguard 跟它同源。所以「走在隊伍最前面」不只是個比方，這個字本來就是這樣用的。
Wiktionary entry for avant-garde (packet evidence kaikki:3f6f69a190036ae4:703307495): From Middle English advaunte-garde, from Old French avant-garde, from avant + garde. Doublet of vanguard.
Two branches
走在前面的作品
把畫面套在作品上：這件作品的位置，比大家習慣的位置還要前面。
adjective · C1
Art, music, writing, film, or design that is avant-garde goes far ahead of what people are used to, trying things nobody has tried, so it can feel strange, difficult, or a little shocking the first time you meet it.
前衛的
走在前面的那群人
同一張圖，鏡頭從作品移到人身上：最前頭那一小群究竟是誰。
adjective · C1
The avant-garde is the set of people — artists, writers, musicians, film-makers and others — who work far ahead of what is usual and bring in new ways of doing things, especially in the arts.
前衛派