The term commonly used to describe a person who is more than a best friend but not a lover is "platonic partner" or "platonic relationship." A platonic partner is someone with whom you share a deep emotional connection and bond that goes beyond a typical friendship, but it doesn't involve romantic or sexual involvement. It's a non-romantic, affectionate relationship based on emotional intimacy, trust, and mutual understanding. This type of connection can be just as valuable and meaningful as a romantic relationship, and it often involves a strong sense of commitment and support for each other.