relating to the time in the evening when most people are watching television, and the cost of advertising is at its most expensive:
• The three major networks' combined share of the prime-time audience has fallen to a new low.
• Warner will have about 20 series on prime-time television in the fall.
— prime time noun [uncountable] :
• The President will address the nation with a televised speech in prime time.
Financial and business terms. 2012.