When texting with someone over IM or SMS that takes too long to reply leaving you waiting and frustrated.

From STEM, an abbreviation short for "Science, Technology, Engineering and Mathematics", a STEMlord is a pejorative term for a particular kind of person who has studied in these areas at university or works in these fields who holds a pretentious, condescending attitude to anyone who has studied in any other fields, particularly the Arts and Humanities. They typically believe themselves to be more "intelligent" and "rational", while generally remaining incredibly ignorant outside of their areas of expertise and having the charisma of a rotting pig's backside.

When you are desperately waiting for a text and you either get a text from a person you don't want it to be or it takes time to come through, one becomes textually frustrated.