Watchful waiting (Also called expectant management.)  - close monitoring of prostate cancer by a physician instead of immediate treatment.

Watermelon stomach - parallel red sores in the stomach that look like the stripes on a watermelon.

Wedge resection of the lung - a small, localized section of the lung is removed, often for a lung biopsy.

Whole blood - blood containing all its components, such as red and white blood cells, platelets, and more.