In my regression one of the control variables has high statistical significance. But when I check the correlation coefficient between this variable and the dependent variable the correlation is almost zero. What is the conclusion that I can derive of this event?
Are you dealing with big data? If you are dealing with big data you may found no (little) correlation between the covariate and the dependent variable, but the estimated coefficient may be statistically significant (however the effect should be very small).
The meaning is that the variable is not significant -unless- other factors in your regression are controlled for.
In the regression: $Y=b_1 x_1+b_2 x_2$
It is possible (and often the case) that simply running $Y=b x_2$ will retrieve nothing of significance, even if $b_2$ is highly significant. This can happen if $x_1$ has a correlation with both $x_2$ and $Y$.