Rapper Zay Hilfigerrr Seen on Video Spraying Roommate with Fire Extinguisher

Zay Hilfigerrr found a new use for a fire extinguisher -- instead of using it to put out a blaze ... he fanned the flames of a feud with his roommate.

The "Juju On That Beat" rapper's seen on video -- obtained by TMZ -- arguing with his roomie off camera with extinguisher in hand ... then taking a few steps toward him and shooting a cloud of fire-squelching chemicals.

Later in the vid ... Zay's heard telling the story of what escalated the dust-up, claiming his roommate accused him of partying and putting a hole in the wall. Zay says his roomie also talked smack about his mom and friends.

The rapper tells us he didn't cause any damage, and was actually getting his stuff to move out when his roommate confronted him along with 3 other guys ... and Zay says everything he did -- including the blast from the fire extinguisher -- was in self-defense.

We broke the story ... cops responded to a 911 call by Hilfigerrr's roommate, who claimed he was being attacked by Zay at their North Hollywood home last week. Police restored the peace while the rapper got his stuff and left.