Lil Wayne -- Sparks Music Deal with Pot Biz ... 'Cause It's 4/20 and Stuff

Lil Wayne may be the one stoner today who is actually productive -- he just dropped a new music vid on the holy day of pot, and in a brilliant biz move he did it with the help of a popular "weed finding" app.

Wayne teamed up with Weedmaps to release, "Hollyweezy," from his mixtape "Sorry for the Wait 2."

We're told Weezy is partnering up with the company -- which pinpoints nearby medical marijuana dispensaries -- because he is a longtime advocate for legalization and reform. Also couldn't hurt that the site will get a ton of traffic on 4/20 ... and therefore more eyes on his video.

Wayne appropriately dropped the vid at 2:20 PM. Just kidding, of course it debuted at 4:20 PM EST.

Now grab your bag of gummy bears and enjoy.

*WARNING -- EXPLICIT LANGUAGE*