the tip and or head of the mals penis. the word is easily formed into a insult by adding another word, forming a compound word "Helmetshiner" or "german army Helmet"
and other things of that nature.although it can be used in a good way like so...
Mike: dude i got the best Helmet last night.
Tyler: she spitshined your Helmet?
Mike: yeah i whipped out my Hoag and she went to town grinding my Helmet
Mike: (yelling at in a movie theatre) hey ho! whatch out, i drank to much soda now i gotta piss!
Gabe: shut the fuck up Helmet-shiner!