A cyclist who, despite biking (and often
even bike commuting) in every imaginable weather condition, refuses to have a pair of mudguards installed on his/her bike. As a result, all of his/her
pants, shirts, jackets, backpacks, etc., are marked by a
long, brown streak down the center.
By extension: A cyclist who, for fear of making himself or his bike seem less pro, refuses to add any accessories to it - accessories that many others consider useful, such as carrier racks, baskets, kickstands, lights, etc.
By extension: A cyclist striving to give of a pretend air of professionalism.