G3921
παρεισδύνω
to infiltrate
παρ-εισ-δύω (also -δύνω), to slip in secretly, steal in: παρεισεδύησαν (vulgar aor.; pass. for act., El., § 19, 2), Ju 4 (cf. also MM, xix).† (AS)
The KJV translates G3921 in the following manner:
are (2x), unawares (2x)
Full Thayer's lexicon entry
παρεισδύνω — pareisdýnō
παρεισδύω or παρεισδύνω: 1 aorist παρεισεδυσα (according to classical usage trans., cf. δύνω; (see below)); to enter secretly, slip in stealthily; to steal in; (A. V. creep in unawares): Jud 1:4 (here WH παρεισεδυησαν, 3 person plural 2 aorist passive (with middle or intransitive force); see their Appendix, p. 170, and cf. Buttmann, 56 (49); Veitch, under the word δύω, at the end); cf. the expressions παρεισδυσιν πλάνης ποιεῖν, the Epistle of Barnabas 2, 10 [ET]; ἔχειν, ibid. 4, 9 [ET]. (Hippocrates, Herodian, 1, 6, 2; 7, 9, 18 (8 edition, Bekker; Philo de spec. legg. § 15); Plutarch, Galen, others.)
1 occurrence