Mand. madba, madbha; plural in -ī, ē but LJLA also -ātā (TgPs 88:4). ENA madbxa, madivxa (so, too, late Nestorian)

To erect an a. → bny, qwm c, ˁbd. To destroy an a. → sḥp, str, ˁqr, pgr. The targums use this word almost exclusively for a Jewish or Israelite altar, using ˀgwr for a pagan one; whereas in OfA the mdbḥ is within the ˀgwr.
DJBA doubts that this is an authentic Babylonian word, but its attestation in Mandaic suggests otherwise.