subpuzzle means A puzzle making up part of a larger puzzle. Lexicurio rates it Rare gem — a strength score of 83 out of 100.
Etymology
From sub- + puzzle.
noun
- A puzzle making up part of a larger puzzle.“The three-dimensional problem consisted of three subpuzzles or sets of pieces; the three subpuzzles (hereafter called parts) could be assembled into one large block.”