A cheese-like gunk or slimey matter that resides under the rim of your penis due to not washing after intercourse or just not cleaning the genitals in general.
In extreme cases, the matter can be green in colour hence the term 'Basil'. Generally occurs after working for days on end and not pulling foreskin aside to clean the head during shower time.
Code name for weed like when ur in school and u need to buy some without getting caught or when you try to tell a story of your "adventures" and u need to say it to the whole world without the popo on ur ass
Hey dude you got the basil?
Ya man i got an ounce in my car!
or
Yo quiero basil! (emphasison the a to sound like a sheep and on the i to make an eeee sound like baaaahhhhhseeeel)