o·ver·bur·den 
(ō′vər-bûrdn)
(ō′vər-bûrdn)tr.v. o·ver·bur·dened, o·ver·bur·den·ing, o·ver·bur·dens
1. To burden with too much weight; overload.
2. To subject to an excessive burden or strain; overtax.
n. (ōvər-bûr′dn)
1. An excessive burden; an overload.
2. Geology
a. Material overlying a useful mineral deposit.
b. Sedimentary rock covering older crystalline layers.
3. Archaeology A sterile stratum overlying a stratum bearing traces of the culture being studied.