User blog comment:Lord Loss/Discussion of the Week: Lances/@comment-4818141-20120615010751/@comment-1758220-20120615021144

To headlock a monster is to repeatedly attack it with enough speed and power that it flinches over and over again before it can do anything. It was a lot more prevalent in 1st and, to an extent, 2nd generation. This video has a good example of it: http://www.youtube.com/watch?v=oYDbkFcaCp4