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.
Constipation is difficulty in passing a stool or less frequent defecation. The feces might be small and hard or it can be of regular size but still hard to pass. Constipation is often seen in infants. It might be a transitory condition. In formula fed infants the constipation might be related to soy formulas.