pigweedPronunciation: /ˈpɪgwiːd/Definition of pigweed noun [mass noun] 1an amaranth that grows as a weed or is used for fodder. Genus Amaranthus, family Amaranthaceae: several species, in particular A. retroflexus and A. albus 2North American term for fat hen.pigweed in other Oxford dictionaries Definition of pigweed in the US English dictionary