When one is too lazy to travel to a toilet and instead uses the most conveniently located container(typically a beer bottle, or empty gallon container)for urination.
I'm not going all the way downstairs to use the bathroom. Instead I think I'll just rock a bottle.
Phrase derived from the traveling game Rock or Potato (where upon seeing an object of questionable nature one member of the group asks Rock or Potato and each member of the group must declare Rock or Potato before approaching the object). This phrase is used to indicate the positive or negative nature of a statement.
"Oh man Jessica, I hooked up with this guy last night..."
"OOOOooh! Rock or Potato? "
"Rock ;)"
"Yeah gurl!"
Playing "go fetch me a rock" is an exercise (often in a corporate context) where someone (e.g. a boss or client) asks you to find or produce some item, product or answer, but they do not provide specific and durable requirements. Then after you bring them the item, they claim it does not satisfy requirements, so you must go fetch another, different, such item. This is tantamount to having requirements change on you after you've delivered the product intended to satisfy the requirements.
"Go fetch me a rock. No, that rock isn't the right kind. Go fetch a bigger rock. No, that rock does not have the right shape. Go fetch a sharper rock." ...and thus you rock fetch ad infinitum.