From Longman Dictionary of Contemporary Englishperfect stranger/fool/angel etcperfect stranger/fool/angel etcused to emphasize that someone has a particular quality completely SYN complete, total I felt a perfect idiot. → perfect
Examples from the Corpus
perfect stranger/fool/angel etc• A year before he had, but that year had changed him, eliminated the sentiment and made him a perfect stranger.• Again he was a person, no longer a perfect stranger.• Asked to stand guard over good or treasure, they would good-naturedly hand everything over to a perfect stranger.• I was then to ask what people thought about being smiled at by a perfect stranger.• She turned into an expert at coaxing food and lodging invitations out of perfect strangers.• Some oranges in a commune, like perfect strangers, dwell upon their own navels, untransformed.• They put money on the table, too, perfect strangers expressing unmistakable monetary interest in the Tonelli Nation. 