Lauryn Hill Concert Video -- Hill Rants About Respect .. After Showing Up Late

If you look up the definition of "irony" ... you'll find this video of Lauryn Hill, who had the nerve to snap at a fan for being disrespectful -- despite the fact SHE was severely late for her own show.

Hill played the House of Blues in Chicago last week, and our HOB sources tells us she was supposed to start playing at 10:30 -- but took her sweet time, and didn't actually make it to the stage until 11:20.

Once she did, most accounts say Lauryn's opening song performance was terrible, and when a fan called her out and flipped her off ... she berated him and had him tossed by security.

The person who shot this video tells TMZ they decided to leave after 2 more songs (which they called "rushed and sloppy") ... and say they saw a huge line of people at the box office asking for a refund.