Meek Mill -- WWE Pissed Off Over Undertaker Entrance Song on Diss Track

Meek Mill can't get a break this week ... after getting trashed for his tepid Drake diss song, he's now in the crosshairs of of The Undertaker over the wrestler's famous ring entrance song.

Meek sampled The Taker's signature bells in the diss track, and the WWE is not amused. A spokesperson tells TMZ, "WWE takes its intellectual property rights very seriously, and we're looking into the matter."

The timing is sure bad ... the WWE is in no mood for clowning, given the tragic death of Rowdy Roddy Piper.