A cheaper brand version of the drug Propecia. A Proscar tablet is usually cut into quarters, each quarter having the same medicinal effect as a Propecia tablet . . . thus the process is cheaper.
Both Propecia and Proscar are brand names of the drug finasteride. Proscar was originally made for disorders of the prostate however.
You can get four times as much Propecia from a Proscar by quarter cutting it.
1) A 5 alpha-reductase inhibitor used in the treatment of BPH.
2) To make reference to having intercourse with a hot girl. Refering to the generic name; finasteride or (fin' as - ta' ride).
Dude 1: Hey man how was your night
Dude2: Freakin sweet, fo sho got me some Proscar