Pater'ros were small pieces of ordnance, now obsolete, worked on swivels; most commonly used on board ships, where they were mounted on the gunwale, and discharged showers of old nails, &c. into hostile boats.
Pater'ros
Chambers's Encyclopaedia, Volume 7: Maltebrun to Pearson, p. 804
Source scan(s): p. 0819