I've seen Ford guys argue this one for years. We have classes that say NO BIG BLOCKS allowed and this subject always comes up.
See you can have a ford 332 Big Block or (see below) you can have a Ford 400 small block. Which bytw fits right in where a 429/ 460 does.
You can just do a Ford big block search and find out all kinds of things. In the end it is just a word used to describe the engine block with a 4.0 inch (or bigger) Ford block and that's all it is.
Big Block - 332/352/360/361/390/406/410/427/428/429/Boss 429/460
General Information
The Ford big-block story centers itself around two primary engine families—the FE-series engines.
FE/FT Series
332/352/361
The “FE” (meaning “Ford Engine”—not “Ford Edsel” or “Ford Engineering”) series big-block was
introduced in 1958 as the 332ci V-8 with a 4.00-inch bore and a 3.30-inch stroke. The 332 debuted
with the larger 352ci big-block. The displacement increase was accomplished by stroking the 332 to
3.50-inches. The FE-series big-block was a hardy Y-block design that lived in many different forms
during its production life which ended in 1976. Use of the FE-series big-block in passenger cars
ended after 1971 with retirement of the 390. The 400M small-block replaced the 390 for 1972 in
passenger cars.