The act of fingering and/or handjob (jerking him off). Some people consider second base to be feeling up too, but that is more or less 1 1/2 bases. The actual base of 2nd is fingering and handjobs. None of that minor stuff, and if you consider feeling up 2nd then you suck and want to pretend you've gone farther than you really have.
We went to 2nd base last night. IT WAS HOT!!!