Definition of Best Friend

An English publication offered a prize for the best definition of a friend and among the thousands of answers received were the following:

“One who multiplies joys, divides grief and sorrow.”
“One who understands our silence.”
“A volume of sympathy bound in cloth and never runs down”

But there is a definition that won the prize:

A best friend is the one who comes in when the whole world has gone out -selected