Justin Bieber Singin' About Sizzurp

Justin Bieber
's so gangsta' these days, he's now droppin' sizzurp similes to describe his interpretation of "love."

The Biebs posted two new songs to SoundCloud -- under the ridiculous name Sir Bizzle -- one of which is an atrocious ballad called "We Were Born for This."  

Biebs has never included sizzurp in his music before ... but threw a reference in his new song: 

but the boys and the girls
they don’t know
what love is like
love is like appreciation
mixed in a double cup of sprite


As TMZ first reported, Bieber has a long connection with sizzurp ... having once been caught on camera in an ATL nightclub holding a double cup

Now, it's clear ... he's not afraid to mix work and play.