RAPPER "TYGA" DUMPS HIS BABYMAMA "BLAC CHYNA" FOR "KYLIE JENNER" KIM KARDASHIAN'S SISTER

Tyga and Kylie Jenner were out together Monday night ... and we're told it was a date, but the way "date" is defined is, well, a sensitive issue.

The youngins went to Kabuki restaurant in Hollywood. Sources close to Tyga tell us they are "dating" but are quick to add that does not mean they are physical. It's important, because he's 25 and she's 17.