Concision is the supreme writing Virtue, but that doesn't mean its pursuit is never misguided or overzealous. Terseness, today's topic, is the misguided variant of false Concision; density, a future topic, is the overzealous variant.
I take the term "terse" from Wayne Schiess (http://tinyurl.com/lsfkbm) to describe misguided Concision because the example he supplies is paradigmatic, and the term evocative, despite the usage being nonstandard. The sentence Wayne describes as terse is: "One of the most prevalent defenses at trial is compliance with [Federal Motor Vehicle Safety Standards]." To display the sentence's "terse and awkward" character, Wayne points out that the skeletal sentence is "The defense is compliance." While the standard senses of "terse" are polished concision and laconic brusqueness, Wayne's meaning accords with etymology: rubbed away. A sentence like this impresses as having rubbed away too much.
Wayne rewrites the sentence, "One of the most prevalent defenses at trial is that the vehicle complies with the Federal Motor Vehicle Safety Standards," but why is this improvement — how does more Concision become outright error? If you're like me, your first thoughts will go to Euphony because of the sentence's "awkwardness," but terseness offends against Euphony only secondarily, the awkwardness rooted in a lack of Clarity. Consider that "the defense was offense" isn't cacophonous — clichés usually are Euphonious — but when "defense" can equate with "offense," both terms denote actions, such as plays in a basketball game. A legal defense isn't an action but something alleged, a proposition, and we express propositions with that clauses. You cannot coherently equate a proposition, a legal defense, with an act of compliance. "The defense is compliance" is formally incoherent, expressing a category error.
The error is similar in origin to excessive passive-voice usage in both errors' coming from a writer stuck in a point of view, instead of orienting to the reader's. Terseness comes primarily from applying the telegraphic speech involved in thinking to the activity of writing, but idiom too can dull writers' sensitivity to terse writing's incoherence. We commit category errors without embarrassment when idiom sanctifies them, but Wayne's correction, not the terse statement he corrected, agrees with both logic and legal idiom. The "terse and awkward" sentence is that way because it is neither coherent nor idiomatic.
(Related entry — Overzealous Concision: Density.)