Porn star Gigi Dior is reacting to a recent defeat in court at the hands of Christian Dior ... telling TMZ it's no sweat off her back because she's used to Big D giving her the shaft.

The adult film actress just finished a years-long legal dispute with the French fashion house after she tried to trademark her stage name ... Dior sued her, and now she won't win the rights to "Gigi Dior."

Gigi tells TMZ ... she knew the odds were against her in her legal war with one of the richest people in the world, Dior owner Bernard Arnault, and while she doesn't agree with the court's decision, she respects it and is taking it in stride.

As Gigi so eloquently puts it ... "I'm used to being shafted by the Big D but this one happens to be Dior." 😆

The porn star says she's going to move on and continue building her Gigi Dior brand ... even without the trademark rights.

Christian Dior successfully argued Gigi was tarnishing their reputation by using "Dior" in pornography ... but Gigi tells us she has NO plans to change her stage name.

Gigi tells us she has no regrets fighting for the trademark -- but she's got a message for Bernard, telling us ... "There's no reason he had to go so hard." No pun intended.