tell on

1 to act upon (a person or a person's feelings) so as to cause a response the pressure of final exams is beginning to tell on the students in the dorm Synonyms impact, impress, influence, move, reach, strike, sway, affect (on), touchRelated Words carry away, dazzle, enrapture, entrance, enthrall (or enthral), ravish, transport; bias, color; inspire, stir; engage, interest, involve, penetrate, pierce; afflict, agitate, bother, concern, discomfort, discompose, disquiet, distress, disturb, fluster, harass, harry, perturb, pester, plague, smite, strain, stress, trouble, try, upset, worry, wring; allure, attract, bewitch, captivate, charm, enchant, fascinateNear Antonyms bore, jade, pall, tire, weary; underwhelm

2 to give information (as to the authorities) about another's improper or unlawful activities in that neighborhood, you wouldn't even think about telling on the drug dealers Synonyms fink, grass (on) [British slang], inform, rat (on), sing, snitch, split (on) [British], squeak, talk, squeal (on)Related Words betray, give away, turn in; backstab, cross, double-cross, sell (out), two-time; blab, tattle; tip (off)