Which term means to speak against in an impassioned manner?

The term that means to speak against in an impassioned manner is "inveigh." This word comes from the Latin root "invehi," which means to carry or to attack. When someone inveighs, they express strong opposition or vehement criticism, often with a sense of urgency or fervor. This characteristic makes "inveigh" particularly suitable for contexts where the speaker is passionately opposing something, such as a policy, an idea, or an action.

In contrast, the other terms do not convey the same meaning. "Jejune" typically describes something that is dull, uninformed, or simplistic, lacking in substance or interest. "Meretricious" refers to things that are flashy or attractive in a superficial way but lack real value or integrity, often used in a disparaging context towards art or literature. "Inveterate" denotes something that is deep-rooted or habitual, often referring to a person’s long-standing habits or tendencies, but does not imply any passionate opposition. Thus, "inveigh" stands out as the correct choice for describing impassioned opposition.