Coined by the MMA website CagePotato.com, "dicknailed" refers to the kind of brutally violent knockout that ends in one fighter lying face down on the canvas, involuntarily planking if you will. For examples of this in the MMA world, see Scott Smith vs. Paul Daley, Josh Neer vs. Mike Pyle, or Siyar Bahadurzada vs. Paulo Thiago.
"Neer goes in for the kill, but out of nowhere Pyle lands a vicious, if not desperate right hand that knocks Neer out cold! Ladies and gentlemen, I do believe the word I’m looking for is “dicknailed”. As in, that poor young man just got dicknailed."
"Thiago rushes in with punches, but Siyar dicknails him coming in with a quick right jab, and Thiago is out cold roughly 40 seconds into the fight."