Sentence:  "Anything else? Yes, Lieutenant Lemmon?" / "Yes, sir," Lemmon drawled. "How do I get out of this chicken-shit outfit?" / "Knock off the <WSD>grabass</WSD>, Glen. Okay, listen up. When you brief your people, make it clear that our mission is defensive only." 
Meaning of the word marked with <WSD> tags:  Rowdy behavior; general horseplay or foolery.