Meaning of river oak in English:
river oak
noun
Any of several Australian trees of the genus Casuarina, or (more widely) the family Casuarinaceae, found on riverbanks or in moist ground, especially C. cunninghamiana, a large tree with needle-like foliage.
Origin
Early 19th century; earliest use found in Allan Cunningham (1784–1842), poet and songwriter.
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