calamitous
Toxic, perhaps.
harmful, damaging
Harmful is an adjective.
you could say 'quickly profused' if its spreading in a bad or harmful way then the word is 'insidious'
There are two syllables in the word harmful. (harm-ful)
The word harmful is an adjective.The adverb form of the word is harmfully.
"Damnum" is the Latin word for harmful or damaging.
The word 'harmful' is not a noun.The word 'harmful' is an adjective, a word used to describe a noun.The noun form of the adjective 'harmful' is harmfulness.The word 'harmful' is the adjective form of the noun harm.The nouns 'harmfulness' and 'harm' are both common, uncountable (mass), abstract nouns; words for concepts.The word 'harm' is also a verb: harm, harms, harming, harmed.
harmful
Another jaguar
it's tame