The Law Enforcement equivalent of Black Lives Matter, aka Blue Lives Matter.

A person that is irrationally compelled to defend all law enforcement officers from accusations of criminal activity, regardless of the evidence presented or the facts.

This type of person often owns Blue Lives Matter merchandise and sees law enforcement as "super heroes".
"Be careful not to mention that pedophile cop news story around Steve. He's a Thin Blue Liner, and I will never hear the end of it."
by Aliel of the New Dawn June 9, 2018
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A female that's crazy- in reference to the movie a thin line between love and hate.
That crazy woman was a thin liner.
by Mullaty December 20, 2014
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