What is the meaning of slog in the sentence: "True friend will slog your face"?
I tracked this down on PoemHunter and the meaning becomes clear in the context of the rest of the poem.
The relevant couplet being:
"Friend knives your back
But true friend will slog your face"
"Stab you in the back" means to harm or betray you in a secret and deceitful way.
"Slog" is used here to mean "hit", "whack".
So, this is how I understand these lines: when friends criticize you, a false friend will do it sneakily, behind your back, but a true friend will do it honestly, directly to your face.
not a teacher