carelessThat was careless of you.
sloppydisapprovingSpelling mistakes always look sloppy in a formal letter.
slapdashinformaldisapprovingHis work is always hurried and slapdash.
rashThat was a rash decision - you didn't think about the costs involved.
thoughtlessThe Prime Minister made a thoughtless remark about the environment.
recklessHe was found guilty of reckless driving.
irresponsibledisapprovingSome dog owners are irresponsible and do not keep dangerous dogs under control.