It is an adjective.
Meaning: uncouth, unpleasant, stupid behavior.It is used to describe the ill mannered behavior of a person and is used in negative sense.
oafishly - adverb.
oafishness - noun
Synonyms: clumsy, awkward, foolish, stupid, rough, boorish, ill-mannered, unrefined, uncultured,lout,moronic,lumpish,idiotic.
Antonyms: smart, clever.
1)She dotes on her son so much that he has become an oafish idiot.
2)Her oafish husband had become a nuisance in the society.
3)His company is suffering because of his oafish act with the client.