From Longman Dictionary of Contemporary Englishcreep up on somebody/something phrasal verb1 SURPRISEDto surprise someone by walking up behind them silently Don’t yell – let’s creep up on them and scare them.2 INCREASE IN ACTIVITY, FEELINGS ETCif a feeling or idea creeps up on you, it gradually increases The feeling she had for Malcolm had crept up on her and taken her by surprise.3 HAPPENto seem to come sooner than you expect Somehow, the end of term had crept up on us. → creep→ See Verb table
Examples from the Corpus
creep up on • But once she was alone with her knitting depression crept up on Leonora like an incoming tide.• It had been creeping up on me during the last couple of days.• In the dark hours before dawn we crept up on our objectives and laid charges.• White bears can creep up on seals much more easily than brown bears can.• Trying to stay calm, he crept up on the statue.• And all the while he had been creeping up on them, unseen.• They must have been creeping up on us.• If you're not careful, this is when lines start to creep up on you. 