A MOF (Mother's Only Friend) is someone who takes the term "tree hugger" to the next level. Not only do they passionately embrace all things green, but they also believe they have a personal relationship with Mother Earth herself. You'll find a MOF composting like it's a competitive sport, carrying reusable bags as if they're fashion statements, and glaring at anyone who dares to use a plastic straw. Essentially, a MOF is the ultimate eco-warrior who treats every day like Earth Day.