The antonyms for "be erect" are many, and they depend on the context in which the phrase is used. In a physical sense, the antonyms could be "be lying down," "be sitting," or "be slouching." In a figurative sense, the antonyms could be "be submissive," "be passive," or "be defeated." The phrase's meaning could also be explicit or implicit, and the antonyms would vary accordingly. Whatever the context, the antonyms would be words that represent the opposite of "be erect" and convey a contrasting idea or feeling.