[1] The headword properly only means the second of these things, but see next note.
[2] Herodotus wrote in Ionic Greek, a dialect in which orv- becomes our-. Additionally, Ionic Greek lost rough breathings via a process called de-aspiration or psilosis. Thus the word o(/ros (from *o(/rvos)--meaning "border"--appears as ou)=ros in Ionic and therefore looks identical to the word that means "guardian". See LSJ s.v. o(/ros (web address 1) for the forms in Ionic and other dialects, with an example from Herodotus (and a suggestion that the aspiration may have been lacking even in dialects without psilosis). The present entry thus reveals something interesting about ancient understanding of the morphology of Greek dialects. For a summary of Herodotus' Ionic dialect, see Flower and Marincola 2002, 44-48.
[3] This non-classical Greek word, a neuter plural, appears in the Glossae in Herodotum omicron2 s.v. ou)/roi and is glossed in Hesychius omicron1278 as "the things dividing the land" (ta\ xwri/zonta th\n gh=n).