Putting off until tomorrow what you should be doing today because its BORING or you have a mental block or something worse (like a deep-seated fear). Solution: get over it (or get counseling). If you'restuck, MOVE.
Ironically what both you and I are doing right now! Common for long nights of studying for chemistry, math, English, Spanish, and eventually caving in to the crap that is public school and college. I am procrastinating while writing a definition of procrastinating. You were the one to look up procrastinating in the first place, so you don't even need a definition, although I gave it to you anyway.
Procrastinating: What you were doing while reading that long ass definition!
What I was doing while writing that long ass definition.