slang To best someone in a spectacular fashion and/or in a way that is humiliating to them. In basketball, to "dunk on" a defender is to perform a slam dunk over them, a move often considered humiliating to the defender. The phrase is commonly used in a passive construction ("(one) got dunked on"). Here's the part of the debate where she really dunks on him by completely destroying his argument. You can't just tweet at this person and make fun of their opinion. If you really want to dunk on them, you have to correct their horrible grammar too.
IMPORTANT NOTE: Feb 2, 2019 - I am currently updating the site to have all the articles on the same format and also shooting new HD videos of the exercises in the library. For the duration of the this update I am selling Game Changers at an 80% discount (YES YOUR READ THAT RIGHT - 80% OFF the regular price). Instead of paying $47 you can pick up a copy of just $9. But hurry - this offer will be gone once I finish the updates.

A second, more efficient and correct method is to use an infrared laser placed at ground level. When an athlete jumps and breaks the plane of the laser with his/her hand, the height at which this occurs is measured. Devices based on United States Patent 5031903, "A vertical jump testing device comprising a plurality of vertically arranged measuring elements each pivotally mounted..." are also common. These devices are used at the highest levels of collegiate and professional performance testing. They are composed of several (roughly 70) 14-inch prongs placed 0.5 inches apart vertically. An athlete will then leap vertically (no running start or step) and make contact with the retractable prongs to mark their leaping ability. This device is used each year at the NFL scouting combine.