sunflower sunflower /ˈsʌnˌflaʊər/ aep /-ˌflaʊr/ noun [C] ► F0 a plant, usually having a very tall stem and a single large, round, flat, yellow flower, with many long, thin, narrow petals close togetherThesaurus+: ↑Flowers and flowering plants , ↑Flowers - general words