Lau Tzu never spoke of enlightenment. Chuang Tzu spoke of the "real person". Both would say that to have life lived through you as you sit passively in wonder would be "The Way". Only when the Buddhists came to China from India with Buddhism did we get this situation where a Taoist could ask "what is Enlightenment?".
To unite solid and spirit as one, mind is matter, matter is mind. Knock Knock, Diiiiing! No duality, no question, no explanation. Just a love and deep sense of awe and wonder for every aspect of the whole, that is IS and you are that, shut up, enjoy. It Is wonderful.