In heraldry an abatement is a mark on a device indicating some form of dishonour. Where abatements are a charge, the tincture of that charge will be one of the stains in order to indicate a stain on the bearer's honour.
Abatements are described by Fox-Davies as one of those pleasant idiocies that has done so much to the detriment of heraldry. In spite of being included in numerous books on heraldry in period, the only abatement that appears to have been used in period is the inverted shield for treachery, and that not willingly (there are extremely isolated occurences of abatements in Scotland in the modern era). It is generally accepted that as it would be better to have no arms at all rather than arms with an abatement, the only place they ever really existed were in heralds' minds.