Deceitful (4106) (plane from planos = deceitful, root idea = has idea of wandering) (Click word study of related verb planao) describes a roaming or a wandering and then figuratively a going astray or a wandering out of the right way. The verbal form planao means to cause to wander off the path, to cause someone to hold a wrong view and so to mislead or deceive. Vincent says plane is an "error which shows itself in action...It may imply deceit as accompanying or causing error" The literal use in the sense of roaming is found in the Greek historian Herodotus who records this note of Solon "who roamed the earth in search of new information". TDNT has the following note on secular uses of plane writing that... The life of men who strive after various things (Critias Fr., 15 [Diels7, II, 381, 20]), indeed, the action of many men (Philodem. Philos. Volumina Rhetorica, VIII, 33) can be called an “error.” In the NT, plane is used only in the figurative sense to describe straying or wandering from the path of truth. The idea of plane is error, delusion, deception. Plane describes a wanderer, as a star or planet that appears not to stay on course. Planes is frequent in Greek secular writings to mean deceit. Aristotle uses plane for mistakes in investigation...Plane used in the active sense of deceit is late and rare (secular Greek). The passive (meaning) "illusion" in seeing and sense perception generally, the vacillation of knowledge found even in wise men, the error which is to be explained by overestimation of a hedone (pleasure) -- all these things can be denoted plane. (Kittel, G., Friedrich, G., & Bromiley, G. W. Theological Dictionary of the New Testament. Eerdmans) Plane in the present verse describes one who wanders from the path of truth, orthodoxy or piety and into error, delusion or deceit. Plane is found 10 times in the NT (Mt 27:64; Ro 1:27; Eph 4:14; 1Thes 2:3; 2Thes 2:11; Ja 5:20; 2Pe 2:18; 3:17; 1Jn. 4:6; Jude 1:11) and 3 times in the Septuagint (LXX) (Pr 14:8, Jer 23:17, Ezek 33:10) Matthew 27:64 "Therefore, give orders for the grave to be made secure until the third day, lest the disciples come and steal Him away and say to the people, 'He has risen from the dead,' and the last deception will be worse than the first." Romans 1:27 (note) and in the same way also the men abandoned the natural function of the woman and burned in their desire toward one another, men with men committing indecent acts and receiving in their own persons the due penalty of their error. Comment: Here plane describes a behavior which deviates seriously from that which is morally correct and in context refers to a "perversion" 1 Thessalonians 2:3 For our exhortation does not come from error or impurity or by way of deceit; 2 Thessalonians 2:11 And for this reason God will send upon them a deluding influence so that they might believe what is false, James 5:20 let him know that he who turns a sinner from the error of his way will save his soul from death, and will cover a multitude of sins. (Comment: Here plane speaks more of conduct that is in error) 2 Peter 2:18 (note) For speaking out arrogant words of vanity they entice by fleshly desires, by sensuality, those who barely escape from the ones who live in error, 2 Peter 3:17 (note) You therefore, beloved, knowing this beforehand, be on your guard lest, being carried away by the error of unprincipled men, you fall from your own steadfastness, 1 John 4:6 We are from God; he who knows God listens to us; he who is not from God does not listen to us. By this we know the spirit of truth and the spirit of error ("the spirit which misleads us to hold the wrong view or be mistaken") Jude 1:11 Woe to them! For they have gone the way of Cain, and for pay they have rushed headlong into the error of Balaam, and perished in the rebellion of Korah. Proverbs 14:8 The wisdom of the prudent is to understand his way, But the folly of fools is deceit.