What term describes a blister that is larger than 1 cm and contains fluid?

The term that describes a blister larger than 1 cm that contains fluid is "bulla." A bulla is typically a fluid-filled lesion that is elevated and can occur on the skin or mucous membranes. It is defined by its size, at greater than 1 cm in diameter, making it distinct from smaller blisters, which are often referred to as vesicles.

In contrast, a cyst refers to a closed sac-like structure that may contain liquid, semi-solid, or gaseous material, but it is not specifically a blister nor is it defined by the presence of fluid under the epidermis.

A wheal is a raised, itchy area of skin that often indicates an allergic reaction and is usually smaller than a bulla. It also does not primarily describe a fluid-filled lesion.

An abscess is a localized collection of pus in a tissue, formed by the breakdown of tissue due to infection, which is distinct from a blister and does not necessarily contain clear fluid.

Therefore, "bulla" is the appropriate term as it specifically represents a larger fluid-filled lesion.