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.
彼はのっぺりした顔で、何を考えているかわからない。
He has a featureless face, so I can't tell what he's thinking.
That character is drawn with a blank expression.
adverb, adverb taking the 'to' particle, noun or participle which takes 'suru'
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形で、山らしい山がない。
The terrain around here is flat and smooth, with no real mountains.