to go stealthily or furtively; to slink

boys sneaking over the orchard wall

to behave in a furtive or servile manner

Brit, informal to tell somebody in authority of another's wrongdoing

sneak on your classmates

to put, bring, or take (something) in a furtive or artful manner

She sneaked a glance at the report

somebody who acts in a stealthy or furtive manner

Brit, informal somebody, esp a schoolchild, who informs on others

(used before a noun) done stealthily, furtively, or without warning