Lexical Definition

‎θρησκεία‎ thrēskeía (thrace-ki'-ah) religion ^G:N-F
from a derivative of ‎θρησκός‎

religion, worshipping.

• ceremonial observance

Abbott-Smith

**† θρησκεία (-κία, T), -ας, ἡ (< θρῆσκος), [in LXX: Wi 14:18, 27, Si 22:5 A, IV Mac 5:6, 13*;]
religion in its external aspect (MM, Exp., xv), worship: Ac 26:5, Ja 1:26, 27; θ. τῶν ἀγγέλων, Col 2:18.†
SYN.: v.s. θρῆσκος.

Abbott-Smith References

Liddell-Scott-Jones

θρησκεία-εία,

Ionic dialect θρησκεία-είη, ἡ, (θρησκείαεύω) religious worship, cult, ritual, ἡ περὶ τὰ ἱρὰ θ. [Refs 5th c.BC+]: plural, rites, [Refs 5th c.BC+]

__2 religion, service of God, [LXX+NT]; ἑκατέρα θ., i.e. Christianity and Paganism, [Refs 4th c.AD+]; θ. τῶν ἀγγέλων worshipping of angels, [NT]
__3 in bad sense, religious formalism, ἀντὶ ὁσιότητος [Refs 1st c.AD+]; θ. βιωτική vulgar superstition, [Refs 2nd c.AD+]

_{LSJ Scripture Refs: Acts.26.5 ☩ Jas.1.26 ☩ Col.2.18}