All serious synonyms

adj serious

• fell — simple past tense of fall.
• formidable — causing fear, apprehension, or dread: a formidable opponent.
• hard — not soft; solid and firm to the touch; unyielding to pressure and impenetrable or almost impenetrable.
• heavy — of great weight; hard to lift or carry: a heavy load.
• laborious — requiring much work, exertion, or perseverance: a laborious undertaking.
• menacing — something that threatens to cause evil, harm, injury, etc.; a threat: Air pollution is a menace to health.
• momentous — of great or far-reaching importance or consequence: a momentous day.
• operose — industrious, as a person.
• pressing — urgent; demanding immediate attention: a pressing need.
• strenuous — characterized by vigorous exertion, as action, efforts, life, etc.: a strenuous afternoon of hunting.
• threatening — tending or intended to menace: threatening gestures.
• ugly — very unattractive or unpleasant to look at; offensive to the sense of beauty; displeasing in appearance.
• worrying — to torment oneself with or suffer from disturbing thoughts; fret.
• no joke — sth serious
• smoking — the visible vapor and gases given off by a burning or smoldering substance, especially the gray, brown, or blackish mixture of gases and suspended carbon particles resulting from the combustion of wood, peat, coal, or other organic matter.
• sobering — not intoxicated or drunk.
• unamusing — pleasantly entertaining or diverting: an amusing speaker.