Examples: Arial HC, IDAutomationHC39M. It seems to show up most strong textfrequently with free fonts.
I don't think this has a broad or general meaning at all (unless perhaps we are strictly talking about barcode fonts). I looked into the font you mentioned, IDAutomationHC39M and here's what I found.
- IDAutomation is the company that made this font.
- H stands for "human-readable"
- C39 is the type of code the barcode is (Code 39)
- M is the size of the font (1 cm)
As confirmation for this, I did some extra digging and found this excerpt regarding their code 39 font:
Contains 48 different Code 39 font versions for optimal compatibility with normal, human-readable, extended and symbol versions.
And to address Arial HC, just about every other font with HC I find is an outline font