A blowjob... that only goes halfway; A blowjob that ends before orgasm and/or ejaculation.
Note: "bi", which refers to a part thereof, begins with B, and is to be used only when describing the incomplete "blowjob".
See also: half-j
"She only gave me a bi-j just to watch me squirm."
"She heard her boyfriend coming up the stairs so it was just a bi-j."
"She only gave me a bi-j so I wouldn't go flaccid before penetrative sexual intercourse."