Final answer:
The clear gelatinous liquid in the posterior cavity of the eyeball is called the vitreous humor, which helps maintain the shape of the eye and allows light to reach the retina.
Step-by-step explanation:
The gelatinous liquid in the posterior cavity of the eyeball that appears clear like glass is known as the vitreous humor. This viscous fluid fills the space between the lens and the retina, playing a crucial role in maintaining the shape of the eye and allowing light to pass through to the retina without obstruction. The structure of the eye includes various components such as the cornea, iris, ciliary body, and lens, which all work together to focus light and support vision.