In roleplay, it means trying to exert too much control over the plot and other characters, usually because the player has no concept of in character or out of character and is there to "win" and satisfy their ego rather than be creative and collaborative. Examples:
1) Invincibility Creating a character so powerful and invulnerable that it cannot take any damage, be incapacitated or hindered, lose a fight, feel pain etc.
2) Dictating other players' responses Swinging a punch and telling the other player that they are down, that they are unconscious, cut, dead or whatever. In sexual roleplay, it might mean dictating someone else's level or signs of arousal.
3) Impossibility Drawing a knife when your hands are tied. Pulling a bow out of your rectum when you're on the ground and hogtied (I wish I were making this up). Drawing a bow out of your rectum at all, come to that. Being held by the hair and with a knife at your throat but whizzing round and slapping your captive and disarming them.
4) Just plain silliness Taking the plot to asinine turns purely to avoid your character having to suffer a misfortune too weak for your manly fictitious self. Being shot at and deflecting the bullet with a penny on a string so that it flies back up the gun nozzle. Again, I wish I were making this up.
5) Anything that is used to let one character force the plot and does not enable the story to be a properly collaborative effort with plausibility.
It's annoying, anti-social, counterproductive and makes you look stupid. Nobody thinks the godmoder is strong, hard, cool or intelligent. We think you have no consideration, no understanding of roleplay and no intelligence whatsoever. Don't do it.