What made you want to look up corpus uteri? Please tell us where you read or heard it (including the quote, if possible).
Confession of judgment is a legal term that refers to a type of contract (or a clause with such a provision) in which a party agrees to let the other party enter a judgment against him or her.
An admission is not the same as a confession. A confession is an acknowledgment of guilt in a criminal case. Admissions usually apply to civil matters; in criminal cases they apply only to matters of fact that do not involve criminal intent.