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The act of engaging in the doggy style position then fingering the female's anus and smearing a residue of her poo across her eyebrows forming a Noel Gallagher like monobrow.

also see dirty elvis, dirty beppe
Stu paid the prostitute an extra tenner and she let him give her a dirty gallagher.
by hairystu January 18, 2007
When a girl is menstrating and a person fingers her and wipes the bloody fingers above her upper lip, which makes a red moustache, like that of an irish man.
something smells like fish. My boyfriend must've given me a Dirty Gallagher
by JackenIt April 28, 2011