Here are two definions that won't be found in any dictionary:
What is a philosopher?
"Everything is perceptually modified by proximity and perspective and philosophy is the capacity to pan in and out at will - and a philosopher is someone who can do this."
Christopher J. Ross - Tunnel Visions: Journeys of an Underground Philosopher (6) p12.
Similarly, What is a gentleman?
"A gentleman is a man who can describe a woman without using his hands."
Unattributed (and perhaps rightly so)