Dried bits of poo left on and around the butthole, formed as a direct result of waiting to long to wipe. Aforementioned "crusties" generally begin to form 10 or more minutes after final defecation (a.k.a. grand finale) has occurred.
Note: Flatulence exacerbates said condition as it tends to promote drying. Drying time dependent on velocity of flatulence, body temperature, external humidity, and PSI.
"Kind sir, I seem to have run out of TP. Could you assist me before I develop poop crusties"
"The recent Polly Shore article in the Times caused me to loose track of time, the result was a great deal of uncomfortable poop crusties."
This florida humidity is awesome, 30 minutes and still no poop crusties.
Crust and stains left in a toilet after flushing. They resemble wet bread bits.
Oh you crackhead, you left poop crusties in the can.