BB...... could be bargain bin, or bargain basement.... but more likely named after the BB Gun - a gun that shoots Ball Bearings.... a bit like an air rifle.... and leaves circular holes in things....
As for cut outs/discounting..... a record company presses up a number of 45s then distributes them on sale or return..... the record flops and the stores return the records... so the record company is stuck with a pile of 45s that they can't sell at full price.....
They offer them to dealers at a discounted price, but marks them (with a drill hole, or the corner of the album sleeve clipped) so that they can't be returned back on the sale or return basis.....
WOOF!