Final answer:
Cyanosis refers to a blue or purple coloration of the skin, indicating insufficient oxygen in the blood, often due to heart defects or conditions impeding oxygen supply.
Step-by-step explanation:
Cyanosis signifies that a patient has oxygen-starved skin. This condition indicates that there is an insufficient supply of oxygenated blood, which can result in a blue or purple coloration of the skin. It is commonly seen in heart conditions such as severe septal defects, including tetralogy of Fallot and patent foramen ovale, which can lead to a baby being referred to as a "blue baby." Cyanosis can occur in other situations where the oxygen supply is compromised, for example, in cases of asthma or a heart attack. However, cyanosis is not caused by exposure to sunlight, cyanide poisoning, or an allergic reaction.