Muggie or muggy is weather-related: Relating to muggy weather, conveying a sense of warmth or stickiness.
Puss is relating to a woman's vagina.
Hence, Muggie Puss is used to describe a warm, sticky pussy.
Girl I love your muggie puss.
Your muggie puss is warm and comfortable.
That girl is sexy, but does she have a muggie puss?