offhand
adjective /ˌɒfˈhænd/
  /ˌɔːfˈhænd/
(disapproving)- not showing much interest in somebody/something in a way that is rude or upsets somebody
- an offhand manner
 - He was very offhand with me.
 
Extra Examples- How can you be so offhand about something so important?
 - ‘Yes, of course,’ she replied in an offhand manner.
 - He was struck by the woman's offhand tone.
 - She seemed offhand about the danger involved.
 
Oxford Collocations DictionaryOffhand is used with these nouns:- comment
 - dismissal
 - manner
 - …