adj.无背的；无靠背的
Rose bushes shoot again after being cut back. 玫瑰丛修剪後还能再长出新枝。
He trudge three hour in the snow to get back home. 他在雪中跋涉三个钟点才回到家。
Do exercise every day and you'll be back in condition. 每天锻炼锻炼，你很快会恢复健康的。
The ship beat back against a monsoon. 船逆着季风艰难地行驶。
I flap the flies away but soon they fly back. 我把苍蝇赶走，但一会儿又飞回来了。
