Lexical Definition

‎παραπίπτω‎ parapíptō (par-ap-ip'-to) to defect ^G:V
from ‎παρά‎ and ‎πίπτω‎

fall away.

• to fall aside, i.e. (figuratively) to apostatize

Abbott-Smith

παρα-πίπτω, [in LXX: Ez 14:13 15:8 18:24 20:27 (מעל), 22:4 (אשׁם), Es 6:10 (נפל hi.), Wi 6:9 12:2, II Mac 10:4 A*;]
1. most freq. (Hdt., Thuc., al.), to fall in one's way, befall.
2. to fall into or in (seq. εἰς, Polyb.; c. dat., II Mac 10:4).
3. to fall away (Ez 14:13 15:8 18:24 20:27 22:4, Wi 6:9 12:2; in Polyb., c. gen.): absol., He 6:6.
4. to fail (λόγος, Es 6:10; cf. I Ki 3:19).†

Abbott-Smith References

Liddell-Scott-Jones

παραπίπτω,

fall beside, ἐγγὺς τῶν τειχῶν -πεπτωκός [Refs 1st c.AD+]; come side to side, [Refs 4th c.BC+]

__2 in Mathematics texts, as passive of παραβάλλω, to be applied, [Refs 3rd c.BC+]
__II fall in one's way, κατὰ τύχην παραπεσοῦσα νηῦς [Refs 5th c.BC+]; π. κατὰ βοήθειαν come in time to aid, [Refs 2nd c.BC+]; ὁπότε καιρὸς παραπέσοι as opportunity offered, [Refs 5th c.BC+]; ὁ παραπεσών the first that comes, ἡ παραπίπτουσα ἀεὶ [ἡδονή] [Refs 5th c.BC+]; ὁ παραπεπτωκὼς λόγος that happened to arise, [Refs]; πᾶν τὸ παραπῖπτον or παραπεσόν all that befalls, [Refs 2nd c.BC+]; κατὰ τὸ -πῖπτον incidentally, [Refs 1st c.BC+]
__II.2 with dative, befall, θαυμαστὸν κτῆμα παραπεσεῖν τοῖς Ἕλλησι fell to their lot, [Refs 5th c.BC+]; π. τῇ πόλει νομοθέτης comes to its aid, [Refs 5th c.BC+]
__III fall, rush in, εἰς τὸ Σαμικόν [Refs 2nd c.BC+]
__IV go astray, err, [Refs 5th c.BC+]; τοῖς ὅλοις πράγμασιν ἀγνοεῖν καὶ π. [Refs 2nd c.BC+]
__IV.b to be mislaid or lost, of a document, [Refs 2nd c.BC+], etc.; σανδάλιον παραπεσόν [Refs 2nd c.AD+]
__IV.2 fall aside or away from, with genitive, τῆς ὁδοῦ [Refs 2nd c.BC+]: absolutely, fall away, [NT]
__V fall down before, cringe, flatter, παραπεπτωκώς [Refs 4th c.BC+]
__VI Astrology texts, to be unfavourably situated, [Refs 2nd c.AD+]

_{LSJ Scripture Refs: Heb.6.6}