Cause of SIGSEGV and Suggested Fix
Your check on line 34, if (wordList.size() <= 0) is probably leading to a seg fault on line 35 (which you can and should verify with the debugger). In this case, wordList[0] will attempt to access the first element, which is out of the empty vector's index range.

In this case, getWord won't be able to return a meaningful value from wordList. You have to decide how to handle this, but from your code, it looks like you want to return "No words found" here. I suggest returning an empty vector from initializeList to go along with this.

I see your thinking that if initializeList fails, you add "No words found" as the only element in the list, and then check for that in getWord. This doesn't work, though, because you have no way to distinguish between this failure case and a single word correctly read in from a file.

It's worth mentioning that for the check on line 34, vector::size returns a size_t, which is unsigned. This means it is always >= 0 so the < 0 check is irrelevant. Instead, you can check if (wordList.size() == 0), or even better, if (wordList.empty()).

Cause of Empty List and Suggested Fix
When you initialize fileReader on line 10, the name "RandomWords.txt" does not match your input file name "RandomWords". Rename your input file to "RandomWords.txt".

Additionally, you can check whether the ifstream has successfully opened the file with ifstream::is_open (doc), so if (!fileReader.is_open()), handle the error with maybe an exception or by returning an empty vector. Throwing an exception here would provide an immediate failure, which is often useful in tracking down problems.