sudden infant death syndrome

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A fatal syndrome that affects sleeping infants under a year old, characterized by a sudden cessation of breathing and thought to be caused by a defect in the central nervous system. Also called crib death.

Wiktionary

1. n. pathology The sudden and unexplained death of an infant aged one month to one year, normally while sleeping.

WordNet 3.0

1. n. sudden and unexpected death of an apparently healthy infant during sleep