Any important situation is serious, and this word is also the opposite of humorous and playful.

If you're frowning, someone might say, "Why so serious?" This is a word for people and situations where there's no fooling around. If you're staring at the computer screen, typing quickly, you look serious. If you are in a car accident, that's a serious situation. Some people are more serious than others. If you're always making jokes and smiling, then you're not that serious. One place everyone needs to be serious is at a funeral home.

Definitions of serious

adj of great consequence

“marriage is a serious matter”
important, of import
of great significance or value

adj requiring effort or concentration; complex and not easy to answer or solve

“raised serious objections to the proposal”
“the plan has a serious flaw”
difficult, hard
not easy; requiring great physical or mental effort to accomplish or comprehend or endure

adj completely lacking in playfulness

sober, unplayful
full of fun and high spirits
coltish, frolicky, frolicsome, rollicking, sportive
given to merry frolicking
devilish, rascally, roguish
playful in an appealingly bold way
elfin, elfish, elvish
usually good-naturedly mischievous
arch, impish, implike, mischievous, pixilated, prankish, puckish, wicked
naughtily or annoyingly playful
frisky, kittenish
playful like a lively kitten
mocking, quizzical, teasing
playfully vexing (especially by ridicule)
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adj appealing to the mind

“a serious book”
appealing to or using the intellect

adj concerned with work or important matters rather than play or trivialities

“a serious student of history”
“a serious attempt to learn to ski”
“gave me a serious look”
“a serious young man”
“are you serious or joking?”
“Don't be so serious!”
earnest, sincere, solemn
characterized by a firm and humorless belief in the validity of your opinions
grave, sedate, sober, solemn
dignified and somber in manner or character and committed to keeping promises
excessively serious
not to be taken lightly
serious-minded, thoughtful
acting with or showing thought and good sense
tending to make sober or more serious
of a substantial character and not frivolous or superficial
not serious in content or attitude or behavior
concerned with or comprehending only what is apparent or obvious; not deep or penetrating emotionally or intellectually
airheaded, dizzy, empty-headed, featherbrained, giddy, light-headed, lightheaded, silly
lacking seriousness; given to frivolity
flighty, flyaway, head-in-the-clouds, scatterbrained
guided by whim and fancy
flippant, light-minded
showing inappropriate levity
idle, light
silly or trivial
intended primarily as entertainment; not serious or profound
concerned with trivialities
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adj causing fear or anxiety by threatening great harm

“a serious wound”
“a serious turn of events”
dangerous, grave, grievous, life-threatening, severe
being in or verging on a state of crisis or emergency

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