Slipper hero ("tøffelhelt") is a
Scandinavian1 term for a "soft man" who is a
hero at home, rather than being one of the hunky
heroes saving
damsels in distress down at the pub. It is most often used as a
derogatory term by other men, and often as an argument to convince someone to come down to the pub rather than staying at home with their
better half. ("Oh, don't be a slipper hero!") Can also be used as an excuse for not going out. ("I'm sorry, I have to be a slipper hero tonight...")
The term is often shortened to just slipper ("tøffel"), and can also be used as a verb; the act of staying home with your spouse or girlfriend rather than going out with the guys. ("Are you slippering out again?")
Searching the web, I've found that the term often means someone dominated by his wife. As one site2 puts it: "A real slipper hero is a man who knows what she wants."
So now you know what to think if someone calls you a slipper...
1: Thanks, Rollo
2: http://www.humorkanari.com/text/tankespinn/tankespinn_16.htm