A person with heart disease.
"The cardiac patient was transferred to a specialized unit for immediate treatment."
"The cardiac was damaged during the stormy night on the water."
Pertaining to the heart.
"The patient was admitted due to severe cardiac arrest caused by a blocked artery."
Cardiac comes from the Latin word cardiacus, which was borrowed from Ancient Greek for "relating to the heart." The term entered English through Middle French and has retained its original meaning ever since.