Definition of hairline
- a hairline bone fracture
The plate had a hairline running across it.
He has a receding hairline.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'hairline.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
: a thin line or crack
: the line where your hair starts on your forehead
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