/,haɪpə'kɒndrɪə; ,haɪpə`kɑndrɪə/ n [U] abnormal and unnecessary anxiety about one's health （过分关心自己的健康而引起的病态的过虑）疑病症, 忧郁症.

n[U]
[Date: 1500-1600; Language: Late Latin;Origin: (plural), 'parts of the body just below the chest' (which was thought to be where hypochondria came from), from Greek, 'parts below the central bone in the chest', from hypo- ( HYPO-) + chondros 'cartilage']
when someone continuously worries that there is something wrong with their health, even when they are not ill