Spirituality has a unique definition for each of us. It is a vast concept that most of us connect to religion nowadays.
In yoga, the same as in Tantra, spirituality is a practical thing. You don't have to believe things, you have to verify them through your own practise.
In Tantra, spirituality starts from individual practise. Theory is just a formula. Here is a video that looks at the difference between religion and spirituality, and explores the practical side of the spiritual path in Yoga.