Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Grūnĭum, v. Grynium.
Grȳnīa, ae, f., and Grȳnĭum (also Grūnium in some editt. of Nep.), ii, n., = Γρύνεια and Γρύνιον,