What term is used to describe a manner of speaking that lacks intellectual depth?

The term that describes a manner of speaking that lacks intellectual depth is "glib." When someone speaks in a glib manner, their words may be smooth and fluent, but they often lack sincerity or genuine thought. This implies a superficiality in their communication; the speaker may come across as being overly confident while not engaging with the topic on a meaningful level. Glib speech may be charming or persuasive, but it often fails to convey deeper insights or consideration of the subject matter at hand.

The other terms do not fit this description. "Goad" refers to provoking or annoying someone, often to stimulate action. "Equivocate" means to be deliberately ambiguous or to speak in such a way that leaves one open to multiple interpretations, which can imply depth rather than a lack of it. "Extemporaneous" relates to speaking or performing without prior preparation, which does not inherently imply a lack of depth; it can refer to well-considered, spontaneous responses. Thus, "glib" is the most accurate choice in defining a manner of speaking that is shallow or lacking intellectual substance.