[1] Something that is e)pika/rsios is therefore at a right angle to something else. This neuter nominative/accusative singular of the adjective has the same or similar glossing in other lexica, including Apollonius' Homeric Lexicon, and see also the scholia to Homer, Odyssey 9.70, where the feminine nominative plural occurs (web address 1).
[2] From a gloss on Herodotus 7.36.1, where he does indeed use the word (of Xerxes spanning the Hellespont with a bridge of ships laid together thus: web address 2). See also Herodotus 1.180.3, of roads running at right angles (web address 3), and 4.101.3, of the distance from one end of Scythia to the other, east to west (web address 4).