Adjective in earnest has 1 sense
- earnest, in earnest, sincere, solemn - characterized by a firm and humorless belief in the validity of your opinions; "both sides were deeply in earnest, even passionate"; "an entirely sincere and cruel tyrant"; "a film with a solemn social message"
Antonym: frivolous (indirect, via serious)
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Adverbial in earnest has 1 sense
- seriously, earnestly, in earnest - in a serious manner; "talking earnestly with his son"; "she started studying snakes in earnest"; "a play dealing seriously with the question of divorce"
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