A huge dump. Can be used in the figurative or literal sense.
Literal: A large messy, rancid, steaming pile of shit often assosciated with late night out drinking.
Figurative: a baseless splattering of nonsense, generally assosciated with someone who doesnt know what they are talking about but obvioulsy likes to hear themself talk. In essence they are spewing bullshit out of their mouth.
Literal: After a late night of miller lights and hot wings i woke up hungover and dragged into work; after about ten minutes at my desk I dropped a steaming boolson in the office bathroom.
Figurative: Last night while chatting up a girl at the bar, my jackass friend came over and dropped a boolson on our conversation about how everyone thinks he is smooth with the ladies.