It's not just the absence of abuse.
It's a relationship where the child is given freedom to grow and develop as an individual. It's a relationship where the parent and child are not each other's only sources of emotional support - that isn't healthy. It's a relationship where the parent accepts the role of parent when the child is young and provides guidance, but gives the child opportunities to learn and grow and recognizes that when the child becomes an adult, he/she is becomes the parent's peer and has the right to make his/her own decisions - even if that means it's not what the parent would have wanted. It's a relationship where the parent allows the child the right to privacy and individuality.
Basically, it's a relationship where the parent doesn't treat the child as a "mini me", friend (in childhood), therapist, or surrogate spouse, and conversely, where the parent doesn't infantilize the child either.