The absence of motile spermatozoa in semen.
Azoospermia may be caused by a defect in spermatogenesis or by a physical obstruction that hinders the sperm to be mixed with the rest of the ejaculatory fluid.
Word origin: a-, without + –zoo– » Greek zôion, animal + –spermia.
Compare: oligozoospermia, polyspermia.
See also: sperm count.