swivel gun
swivel gun is a cannon or weapon type.
Overview
Small cannon mounted on swivel for ease aiming.
In detail
swivel gun is a cannon or weapon type.
Sources
Each source is named with the standing the house places on it, so the evidence can be weighed rather than taken on trust.
reference work · Reputable secondary · Wikipedia
“Swivel gun”, English Wikipedia, consulted as further reading
Consult the sourcereference work · Reputable secondary · Wikidata
Wikidata, structured authority record Q1256431: swivel gun
Consult the source