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Vine's Expository Dictionary of NT Words [1]

1: Εὐλαβής (Strong'S #2126 — Adjective — eulabes — yoo-lab-ace' )

lit., "taking hold well" (eu, "well," lambano, "to take hold"), primarily, "cautious," signifies in the NT, "careful as to the realization of the presence and claims of God, reverencing God, pious, devout;" in  Luke 2:25 it is said of Simeon; in   Acts 2:5 , of certain Jews; in  Acts 8:2 , of those who bore Stephen's body to burial; of Ananias, 22:12 (see No. 2). "In that mingled fear and love which, combined, constitute the piety of man toward God, the Old Testament placed its emphasis on the fear, the New places it on the love (though there was love in the fear of God's saints then, as there must be fear in their love now)," Trench, Syn, xlviii.

2: Εὐσεβής (Strong'S #2152 — Adjective — eusebes — yoo-seb-ace' )

from eu, "well," sebomai, "to reverence," the root seb--- signifying "sacred awe," describes "reverence" exhibited especially in actions, reverence or awe well directed. Among the Greeks it was used, e.g., of practical piety towards parents. In the NT it is used of a pious attitude towards God,  Acts 10:2,7; (in some mss. in  Acts 22:12 ); "godly," in  2—Peter 2:9 . See Godly. In the Sept.,   Proverbs 12:12;  Isaiah 24:16;  26:7;  32:8;  Micah 7:2 .

3: Σέβω (Strong'S #4576 — Verb — sebomai — seb'-om-ahee )

"to feel awe," whether before God or man, "to worship," is translated "devout," in  Acts 13:43 , RV (AV, "religious"); 13:50; 17:4,17. See Worship.

Webster's Dictionary [2]

(1): ( v. t.) Devoted to religion or to religious feelings and duties; absorbed in religious exercises; given to devotion; pious; reverent; religious.

(2): ( n.) A devotional composition, or part of a composition; devotion.

(3): ( n.) A devotee.

(4): ( v. t.) Warmly devoted; hearty; sincere; earnest; as, devout wishes for one's welfare.

(5): ( v. t.) Expressing devotion or piety; as, eyes devout; sighs devout; a devout posture.

King James Dictionary [3]

DEVOUT, a. L. See Devote.

1. Yielding a solemn and reverential attention to God in religious exercises, particularly in prayer.

We must be constant and devout in the worship of God.

2. Pious devoted to religion religious.

Simeon was a just man and devout.  Luke 2 .

Devout men carried Stephen to his burial.  Acts 8 .

3. Expressing devotion or piety as, with eyes devout. 4. Sincere solemn earnest as, you have my devout wishes for your safety.

DEVOUT, n. A devotee. Not used.

Holman Bible Dictionary [4]

 Luke 2:25 Acts 10:2 Acts 22:12

International Standard Bible Encyclopedia [5]

dē̇ - vout ´ (εὐλαβής , eulabḗs , εὐσεβής , eusebḗs , σέβομαι , sébomai , "pious," "dutiful," "reverential"): The word is peculiar to Luke. Applied to Simeon ( Luke 2:25 ), Cornelius ( Acts 10:2 ,  Acts 10:7 ), Ananias ( Acts 22:12 ). "Devout proselytes" ( Acts 13:43 , the King James Version "religious proselytes"), with possible reference to the proselytes of righteousness as distinguished from the proselytes of the gate (see Proselyte ). "Devout women of honorable estate" ( Acts 13:50 ), proselytes to Judaism and wives of the men in high position among the heathen (see Josephus, BJ , II, xx, 2). "Devout Greeks" ( Acts 17:4 ), probably, though not necessarily, proselytes of the gate, heathen by birth, who attended the synagogue services and worshipped God. "Devout persons" ( Acts 17:17 ), proselytes of the gate.