What does "heavy thunderstorm" mean?

Question

Because the weatherman said showers and a heavy thunderstorm. Dose that mean TORNADOS! Or hail, heavy rain, ect.

Answer 1

It's fairly subjective, but typically if there is a threat of tornadoes, weathermen are likely to mention it.  So by heavy thunderstorms he is most likely referring to storms that may produce hail, heavy rain, and gusty winds.  But if you want to be sure, I would check the National Weather Service forecast for your area: http://www.weather.gov

Answer 2

It has a very specific definition.  It means that lightning/thunder are occurring, AND precip is falling at a rate of over 0.3 inches per hour, or 0.03 inches per 6 minutes at the time of the weather observation.

FYI moderate thunderstorm would include rain falling at a rate of 0.11 to 0.3 inches per hour, or more than 0.01 and up to 0.03 inches per hour.

So it doesn't imply that there is a tornado, or even that the thunderstorm is severe.  It just means it is dumping heavy rain.  But if you have a severe storm dropping a tornado, then it's quite likely that it is in a heavy thunderstorm, but not necessarily.