plantar

adj. of or pertaining to the sole of the foot

In sciences dealing with the anatomy of animals, precise anatomical terms of location are necessary for a variety of reasons. Non-scientists often wonder why zoological and human anatomists use complex terminology to describe locations on a body, when common terms like "up", "down", "top" and "bottom" could be used instead.
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Plantar /plan·tar/ pertaining to the sole of the foot. plan·tar adj. Of, relating to, or occurring on the sole. [more]Plantar - Community and Resources

Adjective
1. relating to or occurring on the undersurface of the foot; "plantar warts can be very painful"
(pertainym) sole

v. plant, sow; bury, inter; place, put; offer, cast (insults)