Body Modification is in the simplest, obvious terms: the voluntary (in this context) modification of the human body.
Jon Cobb adds:
- In the not so immediately apparent, a lot of possibilities aren't regarded for what they are: Bodybuilding, yoga's physical aspects and contortion, pilates (a type of exercise that leads to full realization of the elastic potential of the body; you can literally grow an inch or more through loosening up the connective tissues between bones, etc.), martial arts hand conditioning, cosmetic surgery or dentistry, hair removal or adorning or patterning (tribalized chest or forearm shaving patterns can only be so out there to somebody), anorexic, bulimic, or fasting behavior intended not to appease the mind but result in a bodily appearance that better reflects the self image, name it; my wife just suggested fashion (if clothing is worn continually with the primary purpose of adornment and encasement, or possibly negation, it ceases to be both temporary, surface, and necessary, therefore a real modification). We no more "need" to comb or keep our hair, or wear clothes inside our houses, than we need to pierce ourselves, but we do, so we should recognize this gift for what it is. In short, any conscientious deviation from the base form of the nude body.
(Lasting is not included in this definition; for something to serve its purpose and be gone in a short period of time is more valid than keeping something forever that never served its purpose, or worse, had none).