To have a hunch means to have feeling based on your intuition or past experiences. It allows you to make a guess on a certain situation, although the answer may not always be correct.

A "hunch" is, in this case, "a feeling or guess based on intuition". Imagine the following dialogue: -I'm afraid he's not coming today. -Why do you say that? He said he would come! -Well, I can't give you a reason, just call it a hunch.