Maccy is used to describe a person with mesmerising control and delicacy. Whether it is with a football, his ice cold touch on your cheek or the way his fingers slide across the piano while playing his own take on Beethoven’s fifth symphony.
The Maccy is someone who like men but doesn’t admit he likes men. This personality can appear when he’s shagging his mrs’s but doesn’t end up finishing with her, he then has to go into the bathroom and find some gay porn to finish to.
When you are on a desperate trip for food from McDonalds, and you will not settle or give up until that certain food (none other) is in your stomach, hence the "Dash" part. This often follows with a "Maccy Rush" (the feeling you get after you eaten McDonalds food)