look up any word, like donkey punch:
 
1.
An extremely good blow job.
Cathy used those great DSL'S to give me a "knee buckler" last night.
by Eman3737 November 29, 2004
 
2.
An intense orgasm
"I didn't fap or have sex for two whole weeks. When I finally came, it was a knee-buckler!"
by Michael Michael Motorcycle July 31, 2013