innocuous means harmless, an antonym for harmless is dangerous.Click to see full answer. Consequently, what is the word for not harmful?harmless. [ hahrm-lis ] SEE DEFINITION OF harmless. adj.not injurious or dangerous.Additionally, what is the synonym of innocuous? Synonyms: clean, innocent, unobjectionable. Antonyms: pernicious, baneful, deadly, pestilent, vesicatory, offensive, vesicant, corrupting, noxious, harmful, degrading. innocent, innocuous(adj) Also question is, what is the synonym of benign? benign(a.) Synonyms: kind, benevolent, gracious, complaisant, humane, obliging, benignant, good, amiable, friendly, kind-hearted, tender-hearted, of a gentle disposition.Is unharmful a word?adjective. causing or capable of causing harm; injurious: a harmful idea; a harmful habit.