A general interrogatory statement/question: similar in meaning to when, in graphic novels or comic strips, an author draws a character with a speech bubble that contains only punctuation marks.
When spoken aloud, can be further defined by the tone of voice in which it is delivered (eg, into a rhetorical or satiric question).
When texted, can be further defined by the use of punctuation.
A: Look at that!
B: mrf, squigit?
A: At that guy in the penguin suit over there.
A: Let's go out tonight.
B: mrf squigit?
A: well, we could go to a movie.
B: mrf? squigit!
A: I'm just tired of all this #$@#