To excrete feces from the anus by means of bowel movement, name so for its tendril or root-like appearance as it lays at the bottom of the bowl. The term also applies to feces that floats at the top of the bowl, as there are many plants that live atop water.
In a business or formal environment: 'If you will be so kind as to excuse me for just a moment, I must promptly drop root in the nearest lavatory.'
Upon Finishing an Extraordinarily Large Bowel Movement: 'Oh my goodness, I just dropped root like a California redwood! I thought I was going to die!'