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.

Inferior or Undesirable

it means to leave somewhere

Going faster than someone else, particularly in some sort of formal or informal competition ; in driving, running or walking. As in "leave in the dust".

It means the same thing as dirt or anything gross.