n. 25B6; noun
See list at rodent .
(informal) her rat of a husband : SCOUNDREL, wretch, rogue; informal beast, pig, swine, creep, louse, lowlife, scumbag, heel, dog, weasel; N. Amer. informal rat fink; dated cad; informal, dated rotter.
(informal) the most famous rat in mob history : INFORMER, betrayer, stool pigeon; informal snitch, squealer; Brit. informal grass, supergrass, nark, snout; Scottish & N. Irish informal tout; N. Amer. informal fink, stoolie.
25A0; rat on (informal)
we don't rat on our friends : INFORM ON, betray, be unfaithful to, stab in the back; informal tell on, sell down the river, blow the whistle on, squeal on, stitch up, peach on, do the dirty on; Brit. informal grass on, shop; N. Amer. informal rat out, finger.
he ratted on his pledge : BREAK, renege on, go back on, welsh on.