The term "nethermost level" refers to the lowest level or bottommost part of something. It can be used to describe the depths of the ocean, the lowest level of a building, or the least desirable position in a hierarchy. There are several synonyms that can be used in place of this phrase, including "lowest point," "bottom level," "deepest depth," or "base level." Other options may include "rock-bottom," "floor zero," or "subterranean depths." Each of these terms can convey a similar meaning to the phrase "nethermost level" and be used effectively in a variety of contexts.