(of a ship's hoisting tackle) Having the blocks drawn close together so no further movement is possible, as when the tackle is hauled to the utmost.

(by extension) Jammed tightly together; very crowded; completely filled or stuffed.

“Some of Sardinia's gorgeous seaside towns have lately been invaded by builders who erected chockablock housing that catered to middle-income tourists but threatened to spoil the landscape.”

In a crowded manner; as completely or closely as possible.

“His study had books stacked chockablock on every shelf.”