Tristan Thompson is finally opening up about ejecting a fan from an NBA game earlier this season ... explaining he had the man booted from the arena after he claims the guy called Khloe Kardashian "a whore."
The incident went down back in November during a Sacramento Kings road game against the Memphis Grizzlies ... but Tristan and the Kings never explained exactly what happened.
Sacramento head coach Alvin Gentry simply said at the time the heckler was spewing "inappropriate things."
On Wednesday's episode of "Keeping Up With The Kardashians," though, Tristan, in a conversation with Khloe at the gym, revealed what the heckler told him.