When you are so involved with a situation and it is also one that may require assistance; when someone is a little less than waist deep in something; when you are in a situation wher your position is either extremely favorable or extremely unwanted.
"Dude I am sack deep in a sausage fest, get me outta here!"
"Dude, I was sack deep in the mud when i stepped out of my truck."
"Dude, I was sack deep in her all night!"
"Dude, I woke up and realized what i had gotten sack deep in last night!"
When having sex with a person, going "Sackdeep" means going as far as the penis length will allow the person to go.If you have an 8 inch penis your going to drop 8 inches of meat in her before the Ballsack road blocks you from going deeper, because you ran out of Cockmeat to go further than 8 inches.
Yea man Jessica is pissed at me becuse I took her best friend "Sackdeep".
(Example 2) A Donkey Show? You damn right I would let a Donkey take me "Sackdeep" for 22 Pesos and a 6pack of Miller.
(Example 3) Man Ive take 3 of those bitches in the Trailer Park "Sackdeep" now 2 are pregnant