Lolo Jones and Tamar Braxton came thiiis close to throwing hands in the "Celebrity Big Brother" house ... after the Olympian called Tamar a "bitch" during a heated confrontation.
Tensions had been building between the two houseguests for days -- but things finally "popped off" Saturday morning when an argument exploded into real smack talk ... and threats of physical violence.
Tamar -- wearing a weird "Back to the Future" mask -- did NOT back down from Lolo ... telling her, "I am from Baltimore. You do not want that problem.