Alphabetical List

Xeriscape
It means to do landscaping in a way that uses less water. I just like the way this word looks.
Xerothermic
To withstand the power of heat, like surviving in the desert for weeks.
Xoana
A simple, carved image, esp. one in which the original block of stone or wood is readily apparent.
Xylene
An aromatic hydrocarbon consisting of a benzene ring with two methyl substituents.
Yeperdoodle
To agree with someone about something that you think is cool or awesome.
Yinz
This originated in Pittsburgh Pa: Slang for "you all" or ya'll.
YOLO
Y.O.L.O Is an acronym for "You Only Live Once". After a while the person you say it to will get annoyed. The main reason to use this is when you do something stupid and the person beside you says something like "Why did you do that? You'll get in trouble!" "Oh well,Y.O.L.O!" Also a synonym for Carpe Diem, which is Latin for seize the day.
Zabaglione
An Italian dessert (or occasionally beverage) made of egg yolks, sugar and sweet wine.
Zealot
A person who is fanatical and uncompromising in pursuit of their religious, political, or other ideals.
Zeitgeist
This is word that comes from German, meaning "spirit of the times". Not only is this a cool sounding word but it is useful as well.