1. Solway Firth - Noun
2. Solway Firth - Proper noun
a large firth on the west coast of Britain between England and Scotland
Source: WordNetThe Romans retreated to the earlier and stronger Hadrian's Wall in the River Tyne Solway Firth frontier area, this having been constructed around 122. Roman troops, however, penetrated far into the north of modern Scotland several more times. Source: Internet
This was the Treaty of York which defined the boundary between the two kingdoms as running between the Solway Firth (in the west) and the mouth of the River Tweed (in the east). Source: Internet