Antonyms of adj de_rigueur

1 sense of de rigueur

Sense 1
de rigueur -- (required by etiquette or usage or fashion; "instruction as to when and where a silk hat is de rigueur")

INDIRECT (VIA obligatory) -> optional -- (possible but not necessary; left to personal choice)

Similarity of adj de_rigueur

1 sense of de rigueur

Sense 1
de rigueur -- (required by etiquette or usage or fashion; "instruction as to when and where a silk hat is de rigueur")
       => obligatory (vs. optional) -- (morally or legally constraining or binding; "attendance is obligatory"; "an obligatory contribution")