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1.
adjective; To describe someone who frequently makes the jump from what is socially acceptable to what is obviously inappropriate; most commonly occurring as a lewd statement.
"Brandon is a habitual line-crosser... I said his mom had dirty nails and he crossed the line by saying 'YA WELL YO MAMAS SO DIRTY SHE STUCK IN A CUCUMBER AND PULLED OUT A PICKLE! Completely inappropriate!"
by AMBAHMAHRI March 09, 2010