Before something (a word, phrase, name, or specific entity, especially that which is anachronistic) was coined or created. From the French meaning "before the letter." So-called "hipsters" have always existed avant la lettre, but it's only in the last few decades that we've attempted to create a label for them.

Collectively, the artists of a particular era, medium, genre, etc., who represent the most innovate practitioners of that particular art form. He was a member of the avant-garde in Paris, but became disillusioned with the constant quest for original ideas.