Well I think that as language and terminology is not precise (I mean, the dictionary can literally change the use of words to reflect common interpretations) you'll get a very wide range of answers. In my experience, it tends to mean something along the lines of the following:
I think that women are equal, so feminists are just whining / trying to subjugate men.
I believe feminists <insert stereotype of feminists> and don't want to be associated with that.
I think women and men are naturally different and gender roles are correct.
I hate women and want to see them controlled and abused by men.
Saw this term on the other thread started by the 17 year old from America.
I always naively thought that if you believe women should have the vote, be able to work & earn their own money, not be afraid of being raped ever.....etc etc and obviously many many other things that could go on forever. That if you believe these things you are a feminist.
I understand that a person may not choose to identify as a feminist but they ARE one if they believe in these things.
So conversely if you are anti feminist I would expect that you believe women should not be able to vote, work etc.
Have been having a read of some of these threads and seems it's not that black and white. Would love to hear views.