[Meaning] they were heaping.1 "And out of this some were mounding, the others fighting back against the throwers."2
And elsewhere: "and they were mounding 2 mounds, [one?] on each side, as against the wall. The bricks from the houses became a bond of the mound".3
[1] If, as it seems reasonable to suppose, the headword is extracted from the quotations which follow, it is third person plural (rather than the identical first person singular), imperfect, of xo/w. For the glossing verb see under chi 430.