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.

Have Fun!

Holy Fuck!

High Frequency

radio communication services from 1.8 to 29.7 MHz, used for long-range communications, the only band used for worldwide communcations other then mircowave and UHF satellite services

H.F or HF means Heart Failure

Or simply being too full to the point of almost dying.
Severe failure of the heart to function properly, especially as a cause of death.