plural boundaries
1
: something (such as a river, a fence, or an imaginary line) that shows where an area ends and another area begins
Those two trees mark the boundary of our property.
The river forms the country's western boundary.
2
: a point or limit that indicates where two things become different
at/on the boundary between fact and fiction
3
: unofficial rules about what should not be done : limits that define acceptable behavior
You need to set boundaries with your children.
Did he violate the boundaries of the doctor-patient relationship?
They're pushing the boundaries of [=doing things that are unusual in] traditional French cooking.
Cite this Entry
“Boundary.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/boundary. Accessed 16 Oct. 2026.
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