Without humor or expression of happiness; grave in manner or disposition / Important; weighty; not insignificant / Really intending what is said (or planned, etc); in earnest; not jocular or deceiving

(colloquial, dialect) In a serious manner; seriously.

solemn

Alternative form of jocoserious

Taking oneself too seriously, pretentiously and humorlessly convinced of one's own seriousness.

(informal) Intended as a joke but also containing truths meant for reflection later.

(idiomatic) Directs attention to immediately preceding failed attempt at humor.

(manner) In a serious or literal manner. / Gravely; deeply; very much. / Used to attempt to introduce a serious point in a less serious conversation.

The state or quality of being serious.

(transitive) To consider (something /what somebody is saying) important and meaningful.