Someone with nothing
better to do than to spy on their neighbours for signs of petty wrongdoing. A derogatory term for members of the neighbourhood watch and other such organisations.
The term refers to the only sign of their presence - curtains twitching in suburban dwellings as they peek out at whatever might be going on
outside.
Has absolutely nothing to do with homosexuality, except where homosexuality is
illegal and thus something else for the curtain-twitchers to report to the authorities.