From Longman Dictionary of Contemporary Englishsneak up phrasal verbWALKto come near someone very quietly, so that they do not see you until you reach them on/behind etc I wish you wouldn’t sneak up on me like that! → sneak→ See Verb table
Examples from the Corpus
sneak on/behind etc• I imagine it would be virtually impossible to sneak up on an owl.• Deion sneaked up behind the announcer, who was wired for sound, and doused him with ice water.• Tam had complained earlier about how he was for ever sneaking up on them and poking about while they were building the fence.• There was no sneaking up on this man.• Time had sneaked up on us and it was now December.• While we fight the Devil on the theological front, he sneaks up on us from behind.• It sneaks up behind us, unexpectedly, while we are engaged in anything but the pursuit of it.• Advertisements are sneaking up on you from at least three new directions. 