Android Studio exposes developers to -nodpi and -anydpi in various places. For example, if you use the New Resource Directory wizard thing, and you choose to add a density qualifier to the directory, you will see "No Density" (-nodpi) and "Any Density" (-anydpi) options.
Some of you might expect these to be well-documented.
In a word, no.
However, courtesy of a fair amount of experimentation (largely done as part of work on this Stack Overflow question and this answer), their use becomes at least a bit clearer. Many thanks to Stack Overflow user rds for the help!