What might Snape consider cowardice?

[Kemper]

No: HPFGUIDX 163623

In the Chapter discussion, colebiancardi synopsized:

Snape drops the big truth on Harry - he tells Harry that he, Snape, is
the Half-Blood Prince. Harry tells Snape to kill him like he killed
Dumbledore and again he calls Snape a coward. Snape yells at Harry,
his face looking inhuman, "DON'T CALL ME COWARD!"

I, Kemper, wondered in one of my answers, what does Snape consider to
be cowardice?  Even though some have suggested that he loses his cool
hear because of some Marauder issues, I'm having difficulty buying it.

What would Snape consider cowardice acts during the events in the
Lighting Struck Tower or the Flight of the Prince?

Kemper, who realizes his question in the Discussion may have been
overlooked... or probably more accurately, underread