If you’ve heard of a movie synopsis, which gives an overview of the plot, you can guess what synoptic means: summarizing. At the end of your 900-page treatise on morals, try to give a synoptic conclusion to drive your ideas home.
Synoptic can be broken down to syn-, meaning together, and -optic, meaning view or sight. So something that is synoptic pulls everything together. At the end of a long day touring your great aunt’s ancestral home, hearing endless stories about every dinner party she ever gave and all the people that ever stayed there, you might synoptically comment, “Basically she cooks well and has lots of fancy friends.”