'assholes and elbows' refers to working hard at a task. It originated in farm work. If a group of field hands is busy and bent over picking crops, then a supervisor looking out over the group would see nothing but "assholes and elbows".
A derivative term with the same origin and meaning is head down, butt up.
Row boss to field hands: Alright that's enough chit-chat and coffee break! It's time to get back to work and I don't want to see nothing but assholes and elbows until this field is picked clean.
noun: an immature, aimless, broke, unanchored person over the age of 35 who is a spendthrift parasite living off of a rotation of working friends, and who assumes no personalresponsibility, despite many parental contributions,and failed college enrollments.
Lars: "Last night Dick came over and ate the rest of my pizza, drank four beers, and crashed on my couch. He asked me to lend him a $20 for gas."
You: "Dude, he's such an assholescent---toss him."