a fortification 37 miles long across the narrowest part of southern Scotland (between the Firth of Forth and the Firth of Clyde); built in 140 to mark the frontier of the Roman province of Britain
one of several parallel layers of material arranged one on top of another (such as a layer of tissue or cells in an organism or a layer of sedimentary rock)
n
anything that suggests a wall in structure or function or effect