Funny that y'all should bring this up, since I just did some research on what "organic" means to the FDA. Here's my blog post, for those interested:

Fortunately, the FDA has already laid out a series of extremely involved organic food regulations that, with enough delving, answer the question. The regulations (7 CFR Part 205, for all you inquiring minds) state:

1. The term, “organic,” may only be used on labels and in labeling of raw or processed agricultural products, including ingredients, that have been produced and handled in accordance with the regulations in this part. The term, “organic,” may not be used in a product name to modify a nonorganic ingredient in the product.

2. "100% organic" must comprise entirely organic ingredients; just "organic," however, must have "not less than 95 percent organically produced raw or processed agricultural products."

3. To be sold or labeled as “100 percent organic,” “organic,” or “made with organic (specified ingredients or food group(s)),” the product must be produced and handled without the use of:

(a) Synthetic substances and ingredients, except as provided in §205.601 or §205.603;

(b) Nonsynthetic substances prohibited in §205.602 or §205.604;

(c) Nonagricultural substances used in or on processed products, except as otherwise provided in §205.605;

(d) Nonorganic agricultural substances used in or on processed products, except as otherwise provided in §205.606;

(e) Excluded methods, except for vaccines: Provided, That, the vaccines are approved in accordance with §205.600(a);

(f) Ionizing radiation, as described in Food and Drug Administration regulation, 21 CFR 179.26; and

(g) Sewage sludge
Here's a link to my original blog post, which includes citations and links to the actual FDA regulations.

That said, buying local is probably almost as important as buying organic from an environmental standpoint. Plus, as has been pointed out, buying local means often you can talk to the farmers and get a sense of what goes onto their crops. Even farms that aren't certified organic often use very few pesticides and practice good farming techniques that are well worth supporting.