plenum?
 

I know this is a pretty stupid question but what is a plenum? I have seen the word mentioned around but I have no idea what it is.
Thanks,

According to Webster,

An enclosure in which the air is at a pressure greater than that outside the enclosure.

Like in the intake manifold.

Also, if you are turbocharged, they call them turbo hats.

Basically it is the box or unit that sits atop the carb to force the air into the carb from the turbo.

...or it can be called a carb bonnet. ;)

-Error