Phimosis is a medical condition in which the foreskin of the penis of a male cannot be fully retracted. The word derives from the Greek phimos (φῑμός, "muzzle"). The term is confusing because it is used to denote both a physiological stage of development (i.e. not a disease), and a pathological condition (i.e. a condition that causes problems for a person). Elasticity and ambiguity of definition are especially common when referring to infants. Conflicting incidence reports and widely varying post-neonatal circumcision rates reflect looseness in the diagnostic criteria. Phimosis has become a topic of contention in circumcision debates
Phimosis in most but not all infants is physiological rather than pathological, whereas phimosis in older children and adults is more often pathological than physiological. Some have suggested that physiological infantile phimosis be referred to as developmental nonretractility of the foreskin to more clearly distinguish this normal stage of development from pathological forms of phimosis. Different management is appropriate.