A Sly Maguy is someone who is a sneak, sometimes a liar but not necessarily with bad intent.
Usually used to describe friends who you have caught out lying, or doing things behind other peoples backs. People who are a bit sly, misleading, calculating & sometimes will lie to make friends!!

Generally, these people are not bad people, there's just something about them that you know is not quite right! Their actions show a side that makes them come across as a bit two-faced & will do what they can at the time to better themselves! Quite possibly, at the expense of others!

When you eat dirt for the first time and leave your family to build a shack in the woods