Without a chaperone; unaccompanied by a supervisory figure.
From chaperon plus -less (from Old English -lēas, meaning 'without'), a suffix that creates adjectives meaning 'lacking' or 'deprived of'.
The -less suffix is one of English's most productive: you can make it 'careless,' 'helpless,' 'chaperonless'—which meant real scandal in Victorian times!
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