back number

n．过期的报纸或杂志

baby-sitter, baby-sitting, baby-snatcher, baby-talk, babyhood, babyish, Babylonian, baccalaureate, baccarat, bacchanal, baccy, Bach, bachelor, bacillus, back, back and forth, back away, back down, back down off, back down/off, back of, back out of, back road, back room, back seat, back talk, back up, back-bench, back-bencher, back-breaking, back-formation, back-pedal, back-up, back-yard, backache, backbite, backbiter, backbiting, backbone, backchat,