Usage: 3 forms in 4 verses
Form Translated As     In Verse(s)
πετρόβολον a slinger LXX.Job.41.28
πετροβόλουσ for rock throwing LXX.Ezek.13.13
rock throwing LXX.Ezek.13.11
πετροβόλοισ rock slinging LXX.1Sam.14.14

Liddell-Scott-Jones

πετροβόλος (petrobolos) a slinger G:N-M

πετροβόλος-ος

(paroxytone), ον, throwing stones, [Refs 5th c.BC+]

__II substantive πετροβόλοςος, , engine for throwing stones, [LXX+2nd c.BC+]; distinguished from καταπέλτης, [πετροβόλοςους 1st c.BC: Diodorus Siculus Historicus 18.51, compare “IG” 22.468.1): \_neuter\_ πετροβόλοςα (i.e. ὄργανα), opposed to δορυβόλα, 1st c.AD: Josephus Historicus “Antiquitates Judaicae” 9.10.3. ">Refs 2nd c.BC+]
__II.2 sling, variant in [LXX]
__III λίθοι πετρόβολοι hurled as from a sling, of hailstones,[LXX]

LSJ Scripture Refs: LXX.Job.41.19*LXX.1Kgs.14.14LXX.Ezek.13.11