Is there a word for an acronym which spells out one of its component words?
What's that figure of speech in which you use the same word to define its meaning, thereby not really defining it.
Like, "YAML Ain't Markup Language", the expanded form of the abbreviation YAML uses itself in its definition and thus doesn't really define the actual thing.
In this case, though, through negation, it restricts the purview of its meaning to a fairly ascertainable concept. But that's just one example.
In other usages, the definition may or may not convey meaning.
Like in this definition of the Internet, "The Internet, a backward formation of inter-network, is a network of networks."
It's not synecdoche, as I used to think.
For instance a elusive statement like "God is...well, only God can define God." exemplifies it.
It uses the word whose definition is sought in the definition itself, thereby abdicating the responsibility of providing meaning or justification.