tiriyaṃ : [adv.] across; transversely.

A.P. Buddhadatta Mahathera, Concise Pali-English and English-Pali Dictionary [available as digital version from Metta Net, Sri Lanka]

Tiriyaŋ (adv.) [Vedic tiryañc (tiryak) to tiras, see tiro & cp. perhaps Ger. quer=E. thwart, all to *ter in tarati] transversely, obliquely, horizontally (as opp. to uddhaŋ vertically, above, & adho beneath), slanting, across. In combn uddhaŋ adho tiriyaŋ sabbadhi "in all directions whatever" D i.251=A ii.129; similarly uddhaŋ adho t. vâpi majjhe Sn 1055; with uddhaŋ & adho D i.23, 153; Vism 176 (where expld). -- A ii.48; Sn 150, 537; J i.96; It 120; DhA i.40 (dvāra -- majjhe t. across the doorway), 47 (sideways); DA i.312; KhA 248.
   -- taraṇa ferrying across, adj. ˚ā nāvā, a vessel crossing over, a traject Vin iv.65.

Pali-English Dictionary, TW Rhys Davids, William Stede,