a.

1. 简朴的；朴素的；不搀杂的
   He advocates plain living.

   他提倡过简朴的生活。

2. 清楚的；明白的；平易的
   The meaning of the sentence is very plain.

   这句句子的意思十分清楚。

3. 无花纹的
4. 坦白的，直率的
   I must be plain with you.

   我必须坦白地对你说。

5. 【婉】（相貌）平常的；丑的
   The child has a plain face.

   这孩子相貌平常。

6. 完全的，彻底的[Z][B]

ad.

1. 【口】完全地；彻底地
   She's just plain silly.

   她简直傻透了。

2. 清楚地；平易地

n.

1. 平原；旷野[C]
   the Great Plains

   北美大平原

2. 平纹布；素色布[P1]
3. （针织的）平针[U]

adj.

1. not decorated or elaborate; simple or ordinary.
   ▸without a pattern; in only one colour.
   ▸unmarked; without identification:

   a plain envelope.
2. easy to perceive or understand; clear.
   ▸not using concealment or deception; frank:

   he recalled her plain speaking.
3. (of a person) having no pretensions; not remarkable or special.
   ▸(of a woman or girl) not marked by any particular beauty; ordinary-looking.
4. sheer; simple (used for emphasis).
5. (of a knitting stitch) made by putting the needle through the front of the stitch from left to right. Compare with purl¹.

adv.

1. used for emphasis:
   that's just plain stupid.
2. clearly; unequivocally.

n.

v.

1. mourn; lament.
2. complain.