As he lay in bed, face upward, and so covered, with that exception, that he seemed to be nothing but a face — like a conventional cherubim — he looked the queerest object I ever beheld.
When Mrs. Micawber has her sea-legs on — an expression in which I hope there is no conventional impropriety — she will give them, I dare say, "Little Tafflin".
…informed him that they had given his letter their best consideration, ’with a view to the happiness of both parties’ — which I thought rather an alarming expression, not only because of the use they had made of it in relation to the family difference before-mentioned, but because I had (and have all my life) observed that conventional phrases are a sort of fireworks, easily let off, and liable to take a great variety of shapes and colours not at all suggested by their original form.
There are no more uses of "convention" identified with this meaning in the book.
Show samples from other sources
It was once conventional wisdom that the earth was flat.
In most countries, the convention is to shake the head to indicate "no", but in Bulgaria that indicates "yes".