mea cul·pa /ˌmeəˈkʊlpə, ˌmeɑ, ˈkʊl(ˌ)pɑ/
Pec·ca·vi I have sinned; -- used colloquially to express confession or acknowledgment of an offense; -- used rarely, superseded by the approximate equivalent mea culpa.
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mea culpa
n : an acknowledgment of your error or guilt