1. massed, heaped; thick, dense (of fighting) MN.i.86 = Cnd.199#5 (ubhato viyūlḥaṃ sangāmaṃ massed battle on both sides); AN.iii.94, AN.iii.99 (sangāma, cp. SN.iv.308); Ja.vi.275 (balaggāni viyūḷhāni; C. = pabbūḷha-vasena ṭhitāni where pabbūḷha evidently in meaning “sambādha.”
2. put in array, prepared, imminent Ja.ii.336 (maraṇe viyūḷhe = paccupaṭṭhite C.). Cp. saṃyūḷha.

apparently vi + ūḷha, pp. of viyūhati, but mixed in meaning with vi + ūha (of vah) = vyūha