Its meant as motivating yourself to liftheavy and to create a whole lot of Hoo-Haa in the gym, definitely something Ronnie Coleman would say during workouts!
What a hood person says when he/she wants someone to handle his/her lightweight it means they want you to fight a battle for them essentially a small ass person that is not a challenge or they feel they must not condescend to a bitches level.
stemming from a song named "lightweight jammin" by E-40, Clyde Carson and the one and only Husalah Husalah, an individual located in the bay area may or may not be lightweight jammin. One who is lightweight jammin at a party would be getting at the broads, sipping on an alcoholic beverage of one's choice, and puffing on a Swisher sweet with any number of toppings inside.
Dancing Rick: man im dumb high and leanin hardddd.
Huslah: Cuddy is you lightweight jammin?
Dancing Rick: i sure as shit am cutthroat. Just look at my car Hus its dumbwet, i been lightweight jammin!