by sleeping with another man, and it is concealed from her husband and her impurity is undetected (since there is no witness against her and she was not caught in the act),
Jewish Publication Society of America Version (JPS1917) - Numbers 5:13 >and a man lie with her carnally, and it be hid from the eyes of her husband, she being defiled secretly, and there be no witness against her, neither she be taken in the act;