Which term describes a raised, dark red birthmark commonly found on an infant's head?

The term that describes a raised, dark red birthmark commonly found on an infant's head is nevus vasculosus. This type of birthmark, also known as a hemangioma, is characterized by a proliferation of blood vessels. Nevus vasculosus often appears shortly after birth and can be located in various areas of the body, but they are especially notable on the face or scalp.

While port wine stains are also vascular birthmarks, they typically present as flat and do not have the raised or bumpy texture associated with nevus vasculosus. A Mongolian spot is a blue or gray flat birthmark often found on the lower back or buttocks and is not related to the dark red appearance described in the question. Capillary malformations are a more general category of skin lesions that can include various types of vascular birthmarks, but they do not specifically refer to the raised, bulbous nature typical of a nevus vasculosus.

Understanding the type of birthmarks helps in educating parents about what's typical for infants and differentiates between benign vascular lesions and other skin conditions that may require more observation or intervention.