1. (noun) nahui, Alternanthera nahui - a perennial herb of coastal to lowland of seasonally to permanently wet habitats such as lagoon, lake, pond, river, and stream margins. It has also been recorded growing within the lag zone and around burn pools of oligotrophicpeat bogs in Northland and Waikato, and from salt marshes. Also an urban weed in clogged gutters, drains and in damp lawns, verges and parkland.