playing the stock market

[kfredson]

Thanks, Niall.

But I still don't get it--if it's just making a guess, why it's "double-guessing?"
I suspect there must be more connotations attached to it than just making a guess?

Yes, I believe there is a different connotation to "double-guessing." In the stock market you don't want to act just like everyone else. You want to "out-guess" the others. One way to do that is to try to imagine what they are thinking (that is, guessing) and do something different.

It is related to second-guessing, which has been discussed here:
double guessing - WordReference Forums

In fact, I suspect that different people use these words in different ways. Usually we can get a feeling for what they are trying to say by the context of their sentence. It is a matter of nuance.

[AllenMass]

Good & informative tips.The term penny stock refers to any stock that is traded outside one of the major exchanges. The definition of a penny stock is a low priced speculative security.