א"ת, Athbash, a method of interchanging the first letter of the Alphabet (א) with the last (ת), the second (ב) with the last but one (ש), the third from the beginning (ג) with the third from the end (ר), &c. Num. R. s. 13.—Num. R. s. 18 ששך באת"בש בבל Sheshach (Jer. XXV, 26) represents Babel by the rule of athbash