nonserious (adjective) frivolous: trivial, silly
Sinonime: bad, baleful, baneful, corrupt, corruptive, dangerous, deadly, deleterious, destructive, detrimental, evil, fatal, hurtful, infective, lethal, malicious, malignant, mephitic, miasmatic, morbid, mortal, nocuous, noisome, noxious, peccant, pernicious, pestiferous, pestilential,
poison, septic, toxic, toxicant, toxiferous, venomous, vicious, viperous, virulent
Antonime: benevolent,
harmless, non-toxic