Antonyms of adj incumbent_on

1 sense of incumbent on

Sense 1
incumbent on (predicate) -- (morally binding or necessary; "it is incumbent on me to attend")

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

Similarity of adj incumbent_on

1 sense of incumbent on

Sense 1
incumbent on (predicate) -- (morally binding or necessary; "it is incumbent on me to attend")
       => obligatory (vs. optional) -- (morally or legally constraining or binding; "attendance is obligatory"; "an obligatory contribution")