Derogatory term for a contractor who has minimal skill, experience and equipment. Trunk slammer implies the contractor
works out of their car trunk
, with no office or licenses and they will likely be difficult to find if the client is not happy with the work.
My neighbor hired a trunk slammer to build his house deck, and now we are laughing at the unfinished disaster that he spent so much money on.
A person who talks like they are great at a sport or activity but in reality he/she is below average and/or very bad at the respective sport or activity.
Carl tells everyone about how good a golfer he is, but the players at the club refer to him as a trunk slammer.