Usage: 5 forms in 10 verses
Form Translated As     In Verse(s)
οπισθίων posteriors LXX.Exod.26.23LXX.Exod.36.28
οπισθίω posterior LXX.Exod.26.27LXX.Exod.36.32
οπισθίου posterior LXX.Exod.28.26LXX.Exod.39.19
οπίσθια posteriors LXX.1Kgs.7.26LXX.2Chr.4.4
their posteriors LXX.Ezek.8.16
οπίσθιά your posteriors LXX.Jer.13.22

Liddell-Scott-Jones

ὀπίσθιος (opisthios) posterior G:A

ὀπίσθιος-ιος, α, ον,

(compare πρόσθιος) hinder, belonging to the hinder part, [Refs]; τὰ . σκέλεα the hind-legs. [Refs 7th c.BC+]; τένων . the tendo Achillis, [Refs 5th c.BC+]; so ὀπίσθιοςια (i.e. μόρια) [Refs 4th c.BC+]; τὸ . the hinder part, opposed to τὸ πρόσθιον, [Refs]; also of the cheek of animals, [Refs] substantive feminine ὀπισθία, hinder part, [Refs 5th c.BC+]; of stars, following in the daily movement, [Refs 2nd c.AD+]. adverb -ίως[LXX]

LSJ Scripture Refs: LXX.1Kgs.4.18*