the fusion of these two popular uses of "brain":

1) blowjob; head; dome; oral sex
2) the brain-like appearance of a scrotum when pulled through a pant zipper to show to unsuspecting bystanders

coupled with a unique pronunciation of "brain" which incorporates dramatically oscillating vocals has yielded the following definition:

n. oral sex performed on the scrotum; gargling a nutsack; sucking on some balls
"holy shit dude! leslie gave me some steamy brayayain on her front lawn after homecoming!"
by biglrock October 21, 2009
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