Spanish word which can be roughly translated as 'hole' (See also: hollow)
One of those obscure climbing terms used by rock climbers to mean jug, or a hole in the rock.
As a place: Hueco Tanks State Historical Park outside of El Paso, Texas. A Mecca for bouldering (a form of rock climbing) and one of the few redeeming qualities of Texas - y'all can take W back any time now...) The stomping grounds of John Sherman
See: Hueco Tanks