Its an acronym for "I'm so fucking dead"

Used for a substitute {lmao} or (rofl)

It's used in the context of the aforementioned being something humorous or it can be used sarcastically to state how unfunny it is.
"Did you see Joey tribbiani on conan's late night show? It's so funny"

-"yeah I'm watching it (rn) isfd.."

Usain bolt:
Random fan: bet I can beat you in a race
Usain bolt: Isfd
by or nahh November 2, 2019
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