Iggy Azalea -- FUMING MAD ... Over Snoop Dogg Insta Slam

The most random rap feud just broke out -- Iggy Azalea vs. Snoop Dogg ... and it's all over a picture he posted mocking Iggy's makeup-free face.

Snoop posted the Instagram this weekend showing an albino-looking woman with cornrow braids and the caption ... "Iggy Azalea no make up."

The "Fancy" rapper got wind of the pic Monday and blasted Snoop on Twitter, saying ... "why would you post such a mean pic on insta when you send your body guards to ask me for pictures every time we are at shows."

Iggy added, "I'm disappointed you'd be such an ass for no reason."

Snoop hasn't blinked since Iggy went off ... the photo's still up on his IG. Iggy has deleted her twitrage.

To be continued?