"A Rebours" is the French title of the novel "Against Nature" by Joris-Karl Huysmans. In English, the term translates to "against the grain" or "upside-down." Synonyms for "a rebours" that capture its sense of being unconventional or contrary include "against the norm," "unconventional," "unorthodox," "nonconformist," "rebellious," "maverick," "iconoclastic," "subversive," and "countercultural." These synonyms all suggest something that goes against the mainstream or challenges established norms or conventions. In essence, "a rebours" describes something that is different or unusual, often in a way that is unexpected or even frowned upon by society.