I don't like the term "brain fart." I like what it stands for -- not being able to remember or think of something, losing your train of thought mid sentence, etc. It happens to me. A lot.
I heard another, more refined, expression that means the same thing: brain fluff. It's more descriptive for me. I think of that airy batting that comes in stuffed toys and quilted items. That's how my brain feels on many days.