IPA: /ˈsændˌpaɪl/
KK: /sændpaɪl/
A mound or heap of sand, often used for play or construction.
The children built a castle out of the sandpile at the beach.
Sandpile → The word is formed from "sand" (from Old English *sand*, meaning loose granular material) and "pile" (from Old English *pyll*, meaning a heap or mound). A sandpile refers to a heap or mound of sand.
Think of a 'heap' ('pile') made of 'loose granular material' ('sand') — that's what a sandpile is.