Which term best describes a raised lesion or bump on the skin?

The term that best describes a raised lesion or bump on the skin is "wheal." A wheal is characterized by its elevated, rounded appearance and typically results from an allergic reaction or other forms of skin irritation, causing localized swelling. It is often temporary and may come and go quickly, presenting as an area of redness and an itchy sensation.

In contrast, other terms like crust refer to dried serum or blood on the skin's surface, while scale denotes flaky, dry patches often associated with conditions like psoriasis. An ulcer is a deeper loss of skin that extends through the epidermis and into the dermis, leading to a more serious skin condition. Therefore, "wheal" specifically signifies the raised, bump-like characteristic that the question highlights.