seriousness noun
ADJ. deadly, deep, full, great, high He maintained an attitude of high seriousness. | mock | underlying The joke did not obscure the underlying seriousness of his point. | moral
VERB + SERIOUSNESS appreciate, realize, recognize, understand Only later did he realize the full seriousness of his offence. | exaggerate | underestimate | play down | treat sth with The problem was not treated with the seriousness it deserved.
PREP. with ~ She spoke with great seriousness of the hardships she had endured.
PHRASES in all seriousness You can't in all seriousness think they'll give you the job! | take, treat, etc. sth with the utmost seriousness
You can also check other dicts: seriousness (English, 中文解释 ), wordnet sense, Collins Definition