beauty.

question: what defines beauty?
everyone uses the term, beauty, regularly, but how do we actually know what it is when everyones has a different perception about it? i decided to turn to my dictionary, to see how they put it into words. and it said, "the quality present in a thing or person that gives intense pleasure or deep satisfaction to the mind ... arising from sensory manifestations (shape, colour etc.)."
the thing that bugs me about that definition is, what exactly are those qualities that cause this deep satisfaction? is it just programmed in us, as to what the qualities may be? you walk down the street and see two people of completely different size, hair colour and fashion sense. now, what makes one of those people more beautiful than the other? our obvious answer would be the skinner girl, with blonde hair who dresses in designer clothes. rather than the large girl, with red hair who wears skants (skirt and pants in one) with runners. why? why is the blonde girl better than the girl in runners? who decided this and why doesn everyone believe it? was there simply a person in ancient times who one day said, ok this is more beautiful than this, for the sake of it?
some say that what beauty is, is our own personal perception. our own opinion. but, don't we base all other opinions on what we have been taught from people while growing? how is the perception of beauty any different? growing up in a catholic household, you would base you're opinion that god was real, because of what you were taught. so, growing up with people who thought blonde hair and big boobs were beautiful, would influnece what you saw as beauty, right?
i went back to my dictionary again, and noticed synonyms to the word, beauty. and the one word that caught my eye was, perfection. i could not help but laugh. there is not one person i know that does not believe in 'perfect'. we all know that there is no such thing as a perfect relationship, or a perfect person, or a perfect day. so why is there even a word for something that isn't even real?
in maths, when a = b, but b = 0, it means that a = 0. right? so does that mean, if beauty = perfection, and perfection doesn't equal anything, then beauty also does not exist? if that is the case, then why do we bother to fret over the beauty of ourselves, if it doesn't even matter? if it does not even exist?