+1 (emphatic)
I regularly run into the most basic use case for definition lists when note taking: I am often exposed to acronyms (especially) or words, the meaning of which I have to discover. Once I’ve discovered the meaning of an acronym or word, I embed a definition in my note or documentation for future reference.
Additionally, and as many others have stated, I have found that the definition list formatting makes for an excellent FAQ or Q&A section in notes or documentation.
I’m using HTML to achieve this for now, but it’s extremely cumbersome to create and edit compared to the markdown implementation.