It would be really good to have a definition that had some shreds of objectivity to it.
The problem with this is that there is no objectivity. It's not just about the behavior, or the "perpetrator", or the "victim". It's the intersection of all of them and it's basically dependent on how the "victim" interprets certain aspects of the "perpetrator's" behavior- which is hugely biased by the personal characteristics of the "perpetrator". A hot guy walking up to a girl in a bar is flattering. An ugly guy doing the exact same thing is creepy. A confident guy using a line is an segue to flirtation. A nervous guy using the exact same line is creepy.
This makes it really difficult to teach people to not be creepy by telling them specific actions to take or not take. Much more useful would be a guide with certain tests that people could put out there to gauge the "temperature" of social situations before committing to a course of action.
One of the lessons highlighted in the thread "Less Wrong NYC: Case Study of a Successful Rationalist Chapter" is Gender ratio matters.
There have recently been a number of articles addressing one social skills issue that might be affecting this, from the perspective of a geeky/sciencefiction community with similar attributes to LessWrong, and I want to link to these, not just so the people potentially causing problems get to read them, but also so everyone else knows the resource is there and has a name for the problem, which may facilitate wider discussion and make it easier for others to know when to point towards the resources those who would benefit by them.
However before I do, in the light of RedRobot's comment in the "Of Gender and Rationality" thread, I'd like to echo a sentiment from one of the articles, that people exhibiting this behaviour may be of any gender and may victimise upon any gender. And so, while it may be correlated with a particular gender, it is the behaviour that should be focused upon, and turning this thread into bashing of one gender (or defensiveness against perceived bashing) would be unhelpful.
Ok, disclaimers out of the way, here are the links:
Some of those raise deeper issues about rape culture and audience as enabler, but the TLDR summary is:
EDITED TO ADD:
Despite the way some of the links are framed as being addressed to creepers, this post is aimed at least as much at the community as a whole, intended to trigger a discussion on how the community should best go about handling such a problem once identified, with the TLDR being "set of restraints to place on someone who is burning the commons", rather that a complete description that guarantees that anyone who doesn't meet it isn't creepy. (Thank you to jsteinhardt for clearly verbalising the misinterpretation - for discussion see his reply to this post)