Among thousands of other definitions, many of which have already been mentioned, a "slam" is a spoken-word poetry contest. They are high energy and very entertaining. Modern "slam" is connected closely with rap and freestyle rap.
A "slam" is also a work of slam poetry.
Ex. 1: Man, that slam was godly good. Kennesha won, damn, she and and her words . . . damn!"
Ex. 2: I wrote a new slam yesterday .. . wanna see it?