Army-speak. Short for "Situation Report". Given by a high ranking officer that claims he/she wants to either fil a situation report or wants one filed by a subserviant officer.
Office: Private, what's your sitrep?
Private: I've been shot in the privates!
Situational report. Also it could mean what are you doing or where are you.
"I need a SITREP of our truck that fell off the cliff"