To fend off is to drive something away or otherwise defend yourself against something. Fend off attack kittens with a big pillow or fend off hunger with a bowl of popcorn.
You can fend something off literally, as when you fend off a swarm of bees by waving your arms around and running in circles. You can also figuratively fend things off, like when a politician fends off a reporter's questions by changing the subject. Fend off comes from the verb fend, used without the off before about the mid-14th century to mean "defend or guard."