Organic has many definitions, including: natural; free thinking; plant and animal matter; carbon-based molecules; dynamic or constantly changing; and free of synthetic (man-made) chemicals.
Organic gardening - gardening without use of synthetic fertilizers and pesticides and with Best Management Practices
Best Management Practices - Standard horticultural practices that stress cleanliness and monitoring to increase yield while limiting costs and environmental degradation.
Sustainable agriculture - continuous organic gardening using best management practices with minimal materials (mulch, compost, soil, etc.) brought in from outside the growing area. Sustainbale farmers grow organically and recycle the old plant residue into compost to supply nutrients for the next round of crops.