Mea Culpa Law & Legal Definition. Mea culpa is a Latin term that means my fault or my own mistake. It is an acknowledgment of a personal error or fault.The phrase originates in the Confiteor which is a part of the Catholic Mass where sinners acknowledge their failings before God. Confiteor translates as 'I confess'.ea Culpa Law & Legal Definition. Mea culpa is a Latin term that means my fault or my own mistake. It is an acknowledgment of a personal error or fault. The phrase originates in the Confiteor which is a part of the Catholic Mass where sinners acknowledge their failings before God. Confiteor translates as 'I confess'.