The headword is an epic short-vowel subjunctive, apparently from the aorist passive of tre/pw, quoted here from Homer, Odyssey 8.292 (web address 1). The lexicographer, however, seems to be positing a present indicative tra/pw. In other instances, as at Iliad 3.441 and 14.314, the headword form seems to be related to te/rpw "take pleasure" (aorist e)/trapon) and indeed Hesychius glosses it with terfqw=men, aorist passive subjunctive of te/rpw.
[1] First person singular, aorist active subjunctive, of tre/pw. when a verb is called "barytone," the meaning is that it is not a contract verb, so it is not accented on the last syllable.
[2] The question poi= tra/pwmai; (with aorist middle subjunctive) occurs several times in Euripides and elsewhere, but the closest parallel to the quotation here is in Libanius, Declamation 51.1.19: ti/s ge/nwmai; poi= tra/pwmai; "Who should I become? Whither should I turn?"
[3] Second person singular, aorist active subjunctive, presumably quoted from somewhere.