Hi there!
There are many definitions of the word creepy, but I'll give you one.
The definition of creepy, that everyone is familiar with, is:
Unpleasing to the eye; Unbearable to look at; Not very nice in appearance.
I can even give you some sentences that may help you out to understand ''creepy'' better.
"Halloween is the creepiest holiday ever."
"Eww, don't make that face! You look creepy!"
"The house was very creepy."
Hope this helps!
Feel free to message me if you need anymore help! I'd be happy to answer more questions! :D