Definition of ironweed in US English:

ironweed

noun

  • Any of various plants growing as weeds of cultivated land and typically having tough or wiry stems; specifically (a) black or common knapweed, Centaurea nigra (now rare); (b) North American any of several species of the genus Vernonia (family Asteraceae (Compositae)).

Origin

Early 19th century; earliest use found in Thomas Batchelor (1775–1838), farmer and writer on language. From iron + weed.

Pronunciation

ironweed

/ˈʌɪənwiːd/