What is Sly Dog?
1.
A sneaky, devious, or just plain lucky chap who manages to be sneaky, devious, and lucky in an endearing way. Often used as a term of admiration.
"Hugh Hefner is the only man alive to have slept with Marilyn Monroe, Barbie Benton, Anna Nicole Smith, and Pamela Anderson - at the same time! The sly dog."
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2.
someone who is tricky and devious but ridicously handsome
Oh, NL, that sly dog.
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3.
a shifty-eyed individual would be best described as a "sly dog"
omfg George is such a fucking sly dog
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4.
Someone who goes out of their way to screw you over, often doing so in a generally gay/homosexual manner which induces anger.
-Defined elitely by DarkGrieverX
"Man what the FUCK? Peter the fag and the Sly One are so fucking gay, they slept together in the same bed and still don't admit they are homosexual, those SLY DOGS."