Spleenless is an adjective that means lacking courage or the ability to stand up for oneself. There are many synonyms that can be used to describe someone who is spleenless, including spineless, gutless, timid, meek, unassertive, passive, and weak-willed. Other related words include indecisive, vacillating, and wishy-washy. These words are often used to describe people who are unable or unwilling to take a stand or make a decision, preferring to avoid confrontation or responsibility. While some may view spleenless individuals as cowardly, it is important to remember that everyone has their own strengths and weaknesses, and there may be situations where a more passive approach is appropriate.