Don't feel bad about your english when it comes to this sort of thing.
There is no standard definition for that o/c abbreviation but it may be
used in the information you're reading in a common way that only the
context will reveal the meaning. I've seen such an abbreviation mean
variously "open circuit", "on center", "off card" so the exact wording
and context of the article is most important. Post some more of the
paragraph or article and I'm sure we'll all be glad to help.

Gord