When it comes to describing people who lack substance or depth, there are many synonyms for the term "hollow men." These might include words like shallow, vapid, insipid, or vacuous. All of these words suggest a lack of meaningful character or emotions, indicating that the people in question are superficial or lacking in authentic connections with themselves or others. Other potential synonyms might include "empty suits," "phony," or "fake," indicating that these are people who are more concerned with appearances than with substance. Overall, these synonyms all imply a certain emptiness or superficiality that separates these individuals from those who are more genuine, thoughtful, and emotionally connected.