shamefulness, obscenity: behavior so base and indecent that it disgraces a person
This is one of the rarest words in the New Testament, used a single time (Ephesians 5:4) and almost unknown before it, apart from one famous line in Plato that pictures a corrupt soul as full of "ugliness." It is the abstract noun built from an adjective meaning "shameful, base, ugly" (αἰσχρός), and it carries that adjective's whole force: in Greek thinking, what is morally disgraceful and what is aesthetically ugly were the same category, the opposite of what is beautiful and good. So the word names not a single act but a quality, the shameful ugliness of a life or a habit.
The live question is how wide that quality reaches. Paul lists it beside "foolish talk" and "coarse joking," two things plainly about speech, which pulls the word toward meaning something like "filthy talk." But he already had a precise word for obscene speech, αἰσχρολογία, which he or his tradition used elsewhere (Colossians 3:8), and here he reached for the broader word instead. For that reason most standard reference works read it as shameful conduct in general, of which vulgar speech is one prominent example rather than the whole. Chrysostom's ancient summary still fits the evidence best: it condemns what is shameful "in word or in deed."
Because it sits at the head of a short list of things to avoid, the word functions almost as an umbrella: the disgraceful ugliness that a holy community has no room for, showing itself here especially in how people talk.
Disputed
Whether αἰσχρότης in Ephesians 5:4 denotes shameful conduct in general or obscene speech in particular.
- majorityIt names shamefulness as a quality of conduct broadly, of which the two speech-vices that follow are prominent but not exhaustive instances; the author's decision not to reuse the more precise αἰσχρολογία (Col 3:8) is decisive, and the lexica (BDAG, Louw-Nida domain 88.149, LSJ sense II, Spicq) support the wider reading.; BDAG, s.v. αἰσχρότης, 29; Louw and Nida, Greek-English Lexicon, domain 88.149; Markus Barth, Ephesians 4-6 (Anchor Bible, 1974), 2:560-62; Frank Thielman, Ephesians (BECNT, 2010), 330; John Eadie, Commentary on the Epistle to the Ephesians
- minorityIn this context the word is drawn into the speech ethic of the triad and is broadly equivalent to obscene talk, since its two neighbours are unambiguously verbal and the passage thematises Christian speech.; Ernest Best, Ephesians (ICC, 1998); Stephen Fowl, Ephesians (NTL, 2012), 164-67; Ben Witherington III, The Letters to Philemon, the Colossians, and the Ephesians
- contestedA middle position: in context the word describes verbal misconduct, yet its lexical sense genuinely exceeds speech and includes indecent behaviour.; Andrew Lincoln, Ephesians (WBC, 1990); Harold Hoehner, Ephesians: An Exegetical Commentary (Baker, 2002), 654-55