noun
sand hill; dune
Refers to a hill or mound made of sand, whether natural (dune) or man-made (e.g., in a sandbox).
子供たちは公園の砂山で遊んでいる。
The children are playing on the sand hill in the park.
海岸には大きな砂山がいくつもあった。
There were many large dunes on the coast.
砂丘 is a more formal or geographical term for 'sand dune', often used in contexts like 鳥取砂丘 (Tottori Sand Dunes). 砂山 is a more everyday word for any sand hill or mound.
Compound of 砂 (すな, 'sand') and 山 (やま, 'mountain, hill'). The reading さやま is a rare alternate reading, likely a contraction or dialectal variant, but すなやま is the standard.