I remember I entertained a great objection to your adversary, because I took it ill that he should be brought here to pester me with his company.
Resenting this little success more than anything, Drummle, without any threat or warning, pulled his hands out of his pockets, dropped his round shoulders, swore, took up a large glass, and would have flung it at his adversary’s head, but for our entertainer’s dexterously seizing it at the instant when it was raised for that purpose.
There are no more uses of "adversary" in the book.
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Then, again, our military training is in many respects superior to that of our adversaries.
Thucydides -- Pericles’s Funeral Oration
Finally, it was rumored, there would be complete information-sharing among all of these previously disconnected and even adversarial entities, and when they were coordinated, and once all the health data they’d collected was shared, most of this made possible through the Circle and more important, TruYou, viruses could be stopped at their sources, diseases would be tracked to their roots.