Gardener's Dictionary: Self-pollination
Self-pollination (n.): In this form of pollination, the flower has both a stamen and a carpel, and the flower is able to fertilize itself without any aid whatsoever. If you hear that tomato plants are self-pollinating, don't take it literally. Most plants do not do this and need some help from pollinators or wind (these plants are called "self-fertile"). Peanuts, for example, are truly self-pollinating plants.
