Block
Block turns up in 2 fields: railroad, statistics. Here is what it means to the people in each one.
Block in railroad
A group of cars bound for the same destination, kept together so they can be handled as one unit.
Railroads plan their networks around blocks: a train is built as a series of blocks in station order, so each terminal can set out or swap its group of cars with one cut instead of picking through the whole train. Blocking plans decide which cars go into which block at which yard. Signal people use the same word for a stretch of track governed by its own signal, so context decides which one is meant.
"Put the Memphis block right behind the power, they're setting it out first, then the Chicago block goes on the rear."
Block in statistics
Group of experimental runs made under similar conditions, used to remove a known nuisance source such as day, batch or tool.
A block is a set of runs expected to be more alike than runs in different blocks: one day, one raw material lot, one chamber, one operator. Blocking assigns the design's runs to blocks in a planned way, usually confounding a high-order interaction with the block effect, so day-to-day or lot-to-lot differences are pulled out of the error term instead of inflating it. The rule of thumb is to block what you can and randomize what you cannot.
"We can't do all 16 runs on one lot of wafers, so block on lot. Eight runs each, ABCD confounded with blocks."