Jastrow: מָסוֹר

מָסוֹר m. (מָסַר) informer, traitor (delivering Jews into the hands of the Roman government). B. Kam. 119ᵃ ממון מ׳ the property of an informer. Ker. 2ᵇ; B. Kam. 5ᵃ Ms. M. (ed. מוסר, corr. acc.); a. fr.—Pl. מְסוֹרוֹת. Y. Sot. IX, end, 24ᶜ, a. e. מפני המ׳ (studying Greek was forbidden) on account of the informers (whose familiarity with Greek tempted them to treason, v. Bab. Sot. 49ᵇ). R. Hash. 17ᵃ המינין והמ׳ (v. Rabb. D. S. a. l. note 50) the heretics and the informers.—Fem. מָסוֹרָה. Midr. Till. to Ps. XII תהא אומתך מ׳ לך (ed. Bub. אומתיה מסיראה, corr. acc.) may thy own people turn informer against thee; Yalk. Ps. 656 (not אימתך).