From Wiktionary, the free dictionary
From French agacer.
agaci (present agacas, past agacis, future agacos, conditional agacus, volitive agacu)
- to aggravate, annoy, irritate
- to set (someone's teeth) on edge
- agaca (“annoying”)
- agacaĵo (“annoyance (annoying thing)”)
- agaciĝi (“to be(come) annoyed; to be set on edge”)
- agaco (“annoyance, (feeling of irritation)”)