What term could describe a lack of intellectual or emotional depth?

The term that best describes a lack of intellectual or emotional depth is "jejune." This word is often used to characterize ideas, discussions, or expressions that are superficial, uninspiring, or lacking in substance. When something is referred to as jejune, it implies that it lacks complexity and fails to engage in deeper thought or emotion, making it seem trivial or naive.

In contrast, the other terms in the options convey different meanings. "Mendicant" refers to someone who begs for alms, particularly in the context of religious orders. "Inveterate" describes someone deeply ingrained in a particular habit or longstanding condition, often with a negative connotation related to stubbornness. "Inveigh" means to speak or write critically or violently against something, focusing on the act of protest or objection, rather than a lack of depth. Understanding these distinctions helps to clarify why "jejune" is the most fitting choice for describing a lack of intellectual or emotional depth.