circumlocution is the use of an unnecessarily large number of words to express an idea — speaking around a subject rather than naming it directly.
The term covers three fairly different behaviours. The first is plain wordiness, where padding is added without intent. The second is evasion, where the indirection is the point: an official who declines to say a thing plainly is circumlocuting on purpose, and the word carries most of its disapproving weight from this sense. The third is neither careless nor evasive — a speaker who lacks a term, or judges that the audience lacks it, describes the thing instead of naming it. Glossing hyperkalemia as "a high potassium level" is a circumlocution, and in translation and language learning it is treated as a competence rather than a failing.
The noun reached English around 1400 from the Latin circumlocutionem, "a speaking around," built from circum, "around," and locutio, from loqui, "to speak" — the root behind elocution, colloquy, and loquacious. The Latin was itself a loan translation of the Greek periphrasis, which English later borrowed outright, so the same idea arrived in the language twice. Charles Dickens fixed the word's bureaucratic association in Little Dorrit (1857) with the Circumlocution Office, a government department devoted to not answering.
It sits close to several neighbours without matching any of them. Periphrasis is the neutral rhetorical name for the same move, with no implication of excess. A euphemism substitutes a milder expression for a blunt one and may or may not be roundabout. Pleonasm is redundancy inside a phrase rather than a detour around a subject. Its direct opposite is 📝brevity.