I had to look it up. It's supposed to mean a u-turn, but my MIL uses it to replace "the F word"...
I've always heard that described as "flip a b**ch," so I guess I will take d*ck in exchange for that. LOL.
"Broad" is somewhat offensive, but I wouldn't be too bothered. If you pretend not to notice it, he will stop saying it soon enough in exchange for something else that might get a reaction out of you. I do think it's kind of cute and funny, too.
Kids can get away with these things moreso than adults, so he may as well enjoy it while he can! LOL.