2. A juvenile way of measuring how "far" a couple has gotten in terms of sexual activity, drawing an analogy to a game of baseball. Typically, "First Base", "Second Base" and so on refer respectively to tongue kissing, some type of heavy groping, oral sex, and full intercourse. Though the precise definitions have been known to vary.
2. "You went out with Cindy last night? So, dude, did you get to third base with her?"
2. sex bases...
3. the things u tag when your playing like baseball or cricket so your not out
"no, im was on base, DUH"
"yeah, after i tagged you"
2. after the first date, they were on second base
3. "he slid into third base in effort not to get out and to advance to home."