This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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n. Dated form of virulence.

n. Same as virulence.

n. extreme harmfulness (as the capacity of a microorganism to cause disease)

n. extreme hostility

"The fever, though it was October, had scarcely abated; indeed, on the contrary, it seemed to have revived and increased in virulency in consequence of the premature return of many people who had fled on its first appearance, and who in coming back too soon to the infected atmosphere, were less able to withstand contagion than those who had remained."

harmfulness    injuriousness    ill will    hostility