sluggish: a blameworthy dullness and slackness that leaves a person slow to take in what is taught and slow to follow through on it
The word paints a whole-person torpor. In everyday Greek it first described a slow pulse or a plodding pack animal that has to be prodded forward, and from that physical picture it stretched to name a heavy, dull mind and a slack, lazy character. Hebrews leans on both edges at once, and it does so as a diagnosis rather than an insult.
Its two appearances bookend a single stern warning that runs from Hebrews 5:11 to 6:12. The same condition is shown from two sides:
- dulled ears that no longer track what they are taught (Hebrews 5:11)
- slack effort that no longer presses on toward the promise (Hebrews 6:12)
At the start the readers "have become" dull in their hearing; at the close they are urged not to slide into the same slackness in perseverance, but to imitate those who inherit the promise through faith and patient endurance.
The tone is like a physician naming a condition that has set in but can still be cured, which is why the writer picks a word that stings without condemning. It is close to other words for laziness, the neutral "slow" (βραδύς), the blaming "idle" (ἀργός), and the reluctant "lazy" of (ὀκνηρός), and to the sluggard of the wisdom writings (עָצֵל). Against those it is stronger and more settled: it names an ingrained sluggishness that always carries reproach.