1. performance (as opposed to practice); going before an audience or on-air; take
でも今はいいから本番中は頑張れよ。But it's fine for now, so do your best during the performance.
2. game; match
彼は本番に強い選手だ。He is a player who comes through in real matches.
3. high of the season; height (of summer, etc.); actual event (or celebration, etc.); real deal
いよいよ、春本番だな。It's finally the height of spring.
4. penetrative vaginal sex (with a prostitute); unsimulated sex (in an adult movie)
この店は本番禁止です。Full sex is not allowed at this establishment.
5. production environment