のっぺり

adverb, adverb taking the 'to' particle, noun or participle which takes 'suru'

featureless; expressionless; flat; blank

Describes a face or surface lacking distinct features, expression, or character. Often used with 顔 or 表情.

• 彼かれはのっぺりした顔かおで、何なにを考かんがえているかわからない。

  He has a featureless face, so I can't tell what he's thinking.

• そのキャラクターはのっぺりとした表ひょう情じょうで描えがかれている。

  That character is drawn with a blank expression.

adverb, adverb taking the 'to' particle, noun or participle which takes 'suru'

flat; smooth

Describes terrain or a surface that is flat and smooth, lacking bumps or irregularities.

• このあたりはのっぺりした地ち形けいで、山やまらしい山やまがない。

  The terrain around here is flat and smooth, with no real mountains.