mic hog 

In voice-enabled chat rooms, a mic hog is a typically annoying and boring chatter who holds the mic without sharing.

I hate it when the mic hogs get on and drone on and on about their shopping or dogs or pick'em-up trucks.

mic hog by Mo Dixley September 12, 2005

mic hogger 

person with a microphone that won’t share.

alec has been singing for more than 30 minutes now. He really is a mic hogger.

mic hogger by dianistrid May 18, 2016