empty, self-inflating boasting: a pretentious confidence whose claim to control or security outruns what is really true
At its heart this word names a boast that is empty because it claims more than is really true. In everyday Greek it pictured the marketplace fraud who bragged of skills he did not have and wealth he did not own, the swaggering impostor everyone could see through. So it was never simply loud pride: it was pride built on a false picture of oneself, a claim that outran the facts.
The Bible gives this ordinary vice a sharper edge. The boast is not just false but faithless, because the thing being claimed belongs to God. The tyrant who imagines he can command the sea and weigh the mountains, the merchant who announces next year's profits, the comfortable person whose possessions promise a security they cannot deliver, all are boasting as if they, and not God, held the future. It is a quiet way of living as though there were no God at all.
This is why the word turns up in two pointed places. James aims it at businessmen who map out their travels and profits without a thought of whether they will even be alive: their confident scheming is "boasting" that treats tomorrow as a possession (James 4:16). John names "the pride of life" (1 John 2:16) as one of the three pulls of a passing world, the swagger that rests its confidence on what a person owns and shows off. In both, the boast is hollow because the things it trusts, plans and wealth and status, are already slipping away.
It helps to set the word beside its neighbors. It is the outward, spoken face of pride: not the quiet self-importance of ὑπερηφανία, which is proud in thought, nor the aggressive contempt of ὕβρις, which is proud in action, but pride that shows itself off in words. The fault listed in the vice catalogs of Romans and 2 Timothy, the ἀλαζών who talks himself up, is this same vice named as a kind of person rather than as a quality.