Day: A period of twenty-four hours, mostly misspent.
Okay, so that was by Ambrose Bierce, US author. And some more gems from the same guy:
Beauty: The power by which a woman charms a lover and terrifies a husband.
Philosophy: A route of many roads leading from nowhere to nothing.
History: An account mostly false, of events mostly unimportant, which are brought about by rulers mostly knaves, and soldiers mostly fools.
Vote: The instrument and symbol of a freeman's power to make a fool of himself and a wreck of his country.
Future: That period of time in which our affairs prosper, our friends are true and our happiness is assured.
Optimist: A proponent of the doctrine that black is white.
Friendship: A ship big enough to carry two in fair weather, but only one in foul.
Year: A period of three hundred and sixty-five disappointments.
Jealous: Unduly concerned about the preservation of that which can be lost only if not worth keeping.
Liar: A lawyer with a roving commission.
Politics: The conduct of public affairs for private advantage.