麦粉 is the literal compound "wheat + powder." In modern Mainland recipes the more common term is
面粉 ("flour"), which by default also means wheat flour.
麦粉 appears in technical/agricultural writing, in product names like
蒸粗麦粉 (couscous), and in Taiwanese usage. Distinguish
麦粉 from
麦片 ("oat flakes / cereal").
