Heuristic refers to a "preliminary detection" feature that can also detect unknown viruses.
This is due to a complex analysis of the affected code and scanning for virus-specific functions. If the analysed code does meet such characteristics, it is reported as suspect.
This does not mean, however, that the code is a virus for sure; false positives may occur.
Please, send us the files that were heuristically detected for further analysis.
You can send them using the submission form on our website:
http://analysis.avira.com/samples/index.php