The term "nether portion" refers to the lower part of a structure, body part, or area. The antonyms for "nether" are "upper" or "higher," referring to the top or uppermost portion of something. For example, the upper portion of a mountain would be its highest point. Other antonyms for "nether" include "superior," "uppermost," and "topmost." These words all imply a sense of height, altitude, or elevation in relation to a lower or subordinate position. The antonyms for "portion" could include "whole," "entirety," or "totality," referring to an object or area that is not divided or separated into parts.