名詞 sneaker:

1. a canvas shoe with a pliable rubber sole
   同義詞：gym shoe, tennis shoe
2. someone acting as an informer or decoy for the police
   同義詞：fink, snitch, snitcher, stoolpigeon, stool pigeon, stoolie, sneak, canary

形容詞 sneak:

1. marked by quiet and caution and secrecy; taking pains to avoid being observed
   同義詞：furtive, sneak, sneaky, stealthy, surreptitious