What term describes the bottom surface of the foot?

The term that describes the bottom surface of the foot is "plantar." This is derived from the Latin word "planta," meaning the sole of the foot. In anatomical terminology, the plantar surface refers specifically to the area of the foot that makes contact with the ground when standing or walking.

The other terms in the question are associated with different parts of the body. The dorsum refers to the upper surface of the foot or hand. The palmar surface pertains to the palm of the hand. Pedal is a more general term related to the foot in general, but it does not specifically indicate the bottom surface. Thus, "plantar" is the precise and correct term for the underside of the foot.