Found in the earliest Hindu scriptures, the Sanskrit word refers to a religious teacher, master or spiritual guide. Guru also means "heavy" or "weighty" as in heavy with knowledge.
In India, the practice of yoga was passed down from Guru to disciple for generations before it was brought to the West and became readily available upstairs from every Starbucks.
My favourite etymological claim is that "Gu" means darkness and "Ru" means destroyer, as in the destroyer of darkeness and ignorance. The way I interpret that for my own life is that whatever experiences, people, books and teachers guide me out of a low vibration of fear, anxiety, self-pity and judgement and into a lighter state of love, compassion, truth and understanding are Gurus.
I believe that our life is a hero's journey and that the obstacles we face reflect to us our darkness so that we may courageously face it, embrace it and grow from it. Like the symbol of the lotus flower, we make our way through the muddy waters of suffering and eventually - with help, dedication and hard work - rise above our difficulties, coming home to the purity of our true nature: love, light and joy.
It's not an easy journey and none of us can do it alone - nor are we expected to. As the age-old adage says, "when the student is ready, the master will appear", so when you feel ready to face your darkness, ask for help and be open to receiving it. Your Guru may not come in the form of a bearded old man, but have faith that life will put the right teachers on your path.
If you've had a Guru help you on your path at a crucial time in your life, please share your story in the comments below.