" is military slang, probably originating with Vietnam-era Marines
, meaning "in a hurry
" or "very busy
. It's also found its way into general usage, suggesting crowding, confusion and/or panic.
In film, the phrase is most popularly recognized in two Marine contexts. First, Aliens, where Sergeant Apone calls his space Marines to action on waking from hypersleep: "Alright sweethearts, you heard the man and you know the drill, assholes and elbows!" (Incidentally, Al Matthews, the actor portraying Apone, was also the first black U.S. Marine to receive the rank of Sergeant in the Vietnam conflict.)2
The other film in which the phrase is used is 1987's Full Metal Jacket, where drill sergeant Hartman harangues his trainees on the obstacle course: "Quickly ladies! Assholes and elbows! Move it out! Get up there!" (Ronald Lee Ermey, who portrayed Sergeant Hartman, also served as a Marine in Vietnam.)3
1. "USMC Dictionary", http://www.vietvet.org/usmcdict.htm, et al.
2. Internet Movie Database, www.imdb.com
3. op cit.