Khloe was wearing a black shirt with see-thru material around the sleeves and part of her chest area -- and during the interview, her boob slipped into the see-thru section for all to see.
Nobody on the set seemed to notice -- but tons of viewers did ... and they bombarded Khloe's Twitter account with messages about the nip slip.
After the interview -- Khloe tweeted back ... saying, "I had a nip slip and I loved it!" She added, "Thank God! I f**king love nipples!!!!"
