"Withdrawn" grade from an undergraduate class vital to my Master's application I am applying for a Master's in Computer Science for the program of artificial intelligence. I already took a class in A.I. but I got a "W" on it. I wasn't doing very well and wanted to drop the class, I was also taking 20 credits at the time and didn't had the time to put the extra effort. 

How will this be evaluated during my application for a Masters? Should I mention it or defend it anywhere in my application?

Some more background:
I am not really into excuses, but if it helps to better understand why I dropped it. About half the class, dropped the class because the professor was not very good. His grading was unfair, and also for me it felt he had a personal nemesis, because he was also my academic advisor and very often I would disagree in a respectful manner as to what I want to pursue in my degree. I didn't want my GPA to be affected by a C or even F. Also he was not a very effective teacher, but he seems to be very respected in the academia (he has some of his research cited 800+ times). Which I am sure he deserves. 

EDIT: I already graduated and recently been working and had to use AI.
A withdrawal on a course that appears key to your masters' studies is probably a big deal.  It would be one thing if your W was in something more tangential to your onward studies.  But if you have withdrawn from a class in the exact same topic that you now want to study for your masters' degree, you really do need an explanation for it.  And it may hurt your chances.

Unfortunately, you don't have a great story to tell.  It may well be true that the professor was a poor teacher, unfair, and even biased against you.  But you don't really have any way to provide evidence of that.  The admissions committee will just be going on your word.  And unfortunately for you, those are the exact sort of things that poor students tend to say as excuses.  Saying such things is likely to reflect poorly on you rather than justify your W (especially if the professor is respected in the field).  I would avoid saying these things. If you get asked about it, focus on the fact that you were taking too many credits at the time and needed to cut back.

So, what are your options?


You could always just go for it.  This might be a negative on your record, but still you may get accepted into programs anyway--especially if the rest of your track record is excellent.  It would be less worrisome if you have other classes or projects that demonstrate your ability/interest in AI.
Try to fill the gap somehow.  Either by retaking the course, or doing some other research/work in the area to prepare for grad school.