Pigweed can mean any of a number of weedy plants which may be used as pig fodder:Amaranthus species Amaranthus albus, white pigweed, tumble pigweed Amaranthus blitoides, prostrate pigweed Amaranthus californicus, California pigweed Amaranthus fimbriatus, fringed pigweed Amaranthus hybridus, smooth pigweed Amaranthus palmeri, the 'pigweed' resistant to glyphosate in the US Southeast Amaranthus retroflexus, redroot pigweed Chenopodium album white goosefoot Polygonum aviculare Portulaca species