Also known as "Castration Anxiety" is an idea by Sigmund Freud. Freud says that a Castration Complex is a fear, in small boys, that usually develops during the phallic stage of sexual development. The Complex makes the boys think, when seeing female genitalia, that she had her penis cut off as a form of punishment. The Complex turns into an anxiety as the boy thinks the same will happen to him.
On a more profound level, Freud thinks that the boy fears he will ultimately lose his power in society via the loss of his penis.
**I would like to credit MSN Encarta Dictionary for helping me with this term.