sandcastle

UK: /ˈsændkɑːs^əl/ US: (sand′kas′əl, -kä′səl)

WordReference Random House Unabridged Dictionary of American English © 2025

sand•cas•tle  (sand′kas′əl, -kä′səl), n. 

1. a small castlelike structure made of wet sand, as by children at a beach.
2. a plan or idea with little substance.

• sand + castle 1850–55

Collins Concise English Dictionary © HarperCollins Publishers::

sandcastle / ˈsændˌkɑːs^əl/ noun

1. a mass of sand moulded into a castle-like shape, esp as made by a child on the seashore