In the UK, a cut-glass accent is a particularly posh accent. It refers to careful, clear diction that does not drop letters in the way that so many of the lower classes do. It is generally associated with education received in an expensive boarding school, with the accompanying overtones of wealth and refinement. It is broadly synonymous with received pronunciation or the Queen's English, although the phrase 'cut-glass' has an even more snooty overtone.
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