1. To promote or aggrandize the importance, quality, or positive aspects of someone or something. In this usage, a noun or pronoun can be used between "big" and "up." The promoters have really been bigging up this new band, so I hope their concert is as good as we've been led to believe. First impressions are really important, so I'd like it if you could big me up to your boss before I meet her. The committee can try to big up this new shopping center all they want, but we're not buying it, and that's why we're here protesting!

2. To make one's body larger and more muscular, as through weight-training. I was always a really skinny kid, so I got this gym membership so I could really big up. The coach said I needed to big up if I wanted a chance of playing on the varsity team next season. I prefer to focus on my overall health and endurance when I go to the gym, not just bigging up.