1. My fault; a personal acknowledgment that something is one's fault or that he or she is guilty of doing something: "When the writer misspelled the word mottoes as mottos in his printed article, he wrote, 'mea culpa' to his readers the next day."
2. Etymology: Latin, literally, "I am to blame", a phrase from the prayer of confession in the Latin liturgy; mea, "my, mine" and culpa, "fault".