This feud is getting nasty!

The Weeknd just took a jab at Justin Bieber's lovemaking skills in his new song with Nav titled "Some Way." How would he know anything about that subject? Oh wait, the "Starboy" crooner is dating JB's ex Selena Gomez, who obviously talked trash on The Biebs' bedroom moves.

"I think your girl, think your girl, fell in love with me. She say my f*** and my tongue game a remedy," one verse goes. Ouch!

The pop star heartthrob shouldn't be surprised his love rival is upping the ante on their pissing match, since he fired the first shot by calling his music "wack" a couple weeks ago, when news first broke that his "Come & Get It" songstress ex was cozying up to the chart topper.

We can't wait to watch this escalate!