For most units, planning leave is like planning your vacation with a civilian job. You talk with your boss, make sure everything is covered, fill out the forms, get it approved, etc. It's not a big deal. I took a month off to go tour Europe once when I was in the Army.
defecate. 1  to void excrement from the bowels through the anus; have a bowel movement. 2  to become clear of dregs, impurities, etc. 3  to clear of dregs, impurities, etc.; purify; refine.
Shit is an English word that is usually considered vulgar and profane in Modern English. As a noun it refers to fecal matter, and as a verb it means to defecate; in the plural (the shits) it means diarrhea. Shite is also a common variant in British English and Irish English.