底层的英文：
rough coat
understratum

参考例句：

A bottom drawer;the bottom stair.
底层抽屉;底层楼梯

laminar sublayer
层[片]流底层

A bottom layer of nickel catalyst was provided to promote the endothermic reaction of steam and methane
底层镍催化剂促进蒸汽和甲烷的吸热反应。

the submerged tenth
(占英国人口1/10的贫困不堪的)底层阶级

The floor just above the ground floor of a building;a mezzanine.
夹楼位于建筑物底层之上的楼面;夹楼

Because of the intense cold, the subsoil of the tundra remains permanently frozen to a great depth.
由于严寒，冻土带的底层土仍然长久冷冻得很深。

A substratum of rock
底层岩石.

She has rented a suite of rooms on the ground floor.
她租了一套底层的房间。

The downstairs of the two little houses had been entirely refashioned.
两栋小楼的底层已经彻底翻修过。

He put the old books on the bottom shelf.
他将旧书放在底层书架上。

rough是什么意思：
adj. 粗糙的；未经加工的；粗鲁的；狂暴的；粗略的；艰苦的
n. 高低不平的地面；艰苦；未经加工的材料
v. 使粗糙；粗暴对待；草拟
adv. 粗暴地；艰苦地

trees with rough bark; rough ground; a rough ride; rough skin; rough blankets; his unsmooth face; unsmooth writing.
有着粗糙树皮的树；粗糙的地面；粗野的驾驶；粗糙的皮肤；粗毛毯子；不光滑的脸；不流畅的作品。

Rough Bushy eyebrows
浓密的粗眉

Take the rough with the smooth

coat是什么意思：
n. 上衣，外套
v. 为某物涂抹

disliked the make of her coat.
不喜欢她衣服的样式

He wears a coat to rags.
他把外套穿得破烂不堪。

Your coat has split at the seams.
你的上装接缝处裂开了。

understratum是什么意思：
n. 底层