Mary Jane is a different name for Marijuana. Also a song from Rick James which really explains it well.
Lyrics from Mary Jane sung by Rick James...

I'm in love with Mary Jane.
She's my main thing.
She makes me feel alright.
She makes my heart sing.
by R 2 J Through K January 9, 2005
Mary Jane is the hottest girl you will ever meet. She is very sweet and extremely lovable. shes funny and she will have the cutest laugh ever. If you meet a mary jane keep her forever and ever and ever and ever and ever and ever and ever and ever and make her your best friend or your girlfriend!
Omg that mary jane is sooo hot! i love her
by mzhvl; December 30, 2011

Just another street term, not to be confused with the candy.
by ZT May 9, 2005
Another word/phrase for marijuana, It is no particular type of marijuana, just a slang word for it in general. Also can be shortened as just Mary, not Mary Jane
I was Smokin' that Mary-Jane Yesterday.

Mary got ya paranoid.
by G-Fo March 3, 2005
Mary Jane is a private school girl that excels at everything. That includes studying, swimming, and art. Especially art. She has a very big future planned ahead of her. She also has a great sense of witty humour and a pretty all teeth smile. Mary Jane has a great easy going personality and she is perfect for being a friendlike lover. Especially since she enjoys the little fun stuff like just chilling and having icecream. She may also be very honest and blunt. She also has a great sense of style. However although she may seem confident and perfect she is actually very insecure about loving and she wants a guy that would love her for who she is. She is probably also insecure about her body. She wants a guy to be devoted and communicative. Don't call her marijuana.
I'm thinking about asking Mary Jane out. She is amazing and real with people. I hope she goes out with me.
by Loyola2018 January 4, 2016
Slang for marijuana. It originates from the Spanish language. Literally
"Let's smoke that bowl, hit the bong,
And then take that finger off of that hole,
Plug it, unplug it,
Don't straaaain, I love you Mary Jane,
She never complains, when I hit Mary,
With that flame, I light up the cherry,
She's so good to me, when I pack a fresh bowl I clean the
-Cypress Hill; Hits from the Bong; Black Sunday
by azrael March 23, 2005
nickname for marijuana; many singers use this in their songs
"Last dance with Mary jane, one more time to kil the pain..."
-Tom Petty
by Mr. Ed March 8, 2005