VERB referring to the acting of rubbing/humping one's crotch and/or bum on someone's belongings. The victim of a Dirty Dog is typically unaware, and it is typically done to a belonging that they would put their face on - often, a pillow. Some victims never know. Others are told by a proud and mocking perpetrator.
Every night, while her sister Fiona was in the shower, Deirdre would Dirty Dog Fiona's pillow. It was her only revenge for her older sister's bullying.