What is the meaning of ?

boundary

a bounded area or region

a bounded group of people, a society, a world as a social grouping, such as business, celebrities, or finance

the border edge of a thing

the category of a thing

the world or realm of a thing

lines drawn between the lines of a text, as on lined writing paper

lines drawn to lay out a draft of a piece of artwork: a sketch

a kingdom

a stratum corresponding to a geologic age

Source: wiktionary.org