The phrase refers to content focused on interactions with unrealistic size differences, typically in an SFW fashion. As the name implies, these interactions usually happen with a giant character, and a tiny character, though ordinary human-sized characters are generally accepted in the mix.
"Isn't gianttiny content fetishy?"
"Nah bruh, you're probably thinking of macrophilia or giantess. Most gianttiny content is meant to be cute, scary or funny."
slip of the tongue perhaps,
Those idiots who drive around in a ridiculously raised pick up truck, making a top heavy vehicle even more top heavy and unstable
A:*gah*
B: "Whats the matter"
A: This dam prickup is blinding me.
B: Stupid thing's, as if there lights weren't blinding enough as it is.