The Greek apatē means deceit, deception, delusion, or the pleasurable illusion that leads one astray. It is not merely lying but the seductive power of falsehood — the attractiveness of what turns out to be empty and destructive.
Paul's warning about 'the deceitfulness (apatē) of sin' (Hebrews 3:13) is a profound pastoral insight: sin doesn't announce itself as sin. It comes disguised as pleasure, freedom, love, progress, or reason. The Parable of the Sower identifies 'the deceitfulness of wealth' (apatē tou ploutou, Matthew 13:22; Mark 4:19) as a thorny weed that chokes the word. Colossians 2:8 warns against 'hollow and deceptive (apatē) philosophy.' Ephesians 4:22 locates the root of sin in 'deceitful desires' (epithumias tēs apatēs). The antidote is truth — knowing Christ, who is the Truth (John 14:6), and having minds renewed by His word (Ephesians 4:23-24).