A lunchbag letdown occurs when something you had been looking forward to turns out to be far worse than originally anticipated.
The term originates in the lunchroom (be it school or office or otherwise) where after a long hard day someone sits down with their lunchbag hoping for something tasty. Instead they find something unappetizing, whether it be the wronglunch, it's moldy, it's cold, or any other multitude of problems.
After such a situation, it can be said that your lunchbag was indeed a let down.
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.
"Base we've got some square groupers floating outside of Miami harbor."