go big or go home

"In poker, the term "all-in" means that a player has put the last of their chips into the pot. When a player is "all-in", they can not perform another action because they don't have any chips left. 

By pushing "all-in", you committed all of your chips to the pot. If somebody had called you and had you "covered" (meaning, had as many chips as you did), then you could have potentially lost your entire stack."
- from http://www.poker-king.com (because that site is totally legit, y'all)