most often associated with purebred. same advantages, same disadvantages... I'm sure the 'actual' definition is different...
Personally, when I think of straight bred, I think of straight xxx bred.. As in produced by a producer, but the only genetics in it's pedigree are from a different, but the same producer.. Like I buy a heifer from joe blow down the road, and always buy my bulls from him.. and even in 4 or 5 generations-- my animals are still straight bred joe blow.