When something is chockablock, it's full or stuffed with something. Cities are chockablock with people.
This humorous-looking, rhyming word means jam-packed. A library is chockablock with books. Malls are chockablock with stores and teenagers. Concerts for popular bands are chockablock with screaming, adoring fans. The beach is chockablock with people during the summer. The opposite of chockablock would be empty, sparse, or deserted. Originally, this was a nautical word for pulley blocks that were touching each other, which led to it meaning crowded and dense. Chockablock means about the same as "chock full."