How would you describe true humility?

Fascinating question.

I'd suggest reading Dickens' David Copperfield and focusing on the character of Uriah Heep for some interesting insight into the psychology of 'humility' in quotes.

Real humility: pondering the vastness of the unknown in nature and realizing how little you know and how irrelevant most of your beliefs,desires and intentions are.

Among humans, I find that humility = sense of humor is often a good approximation.