dumb-assadjective
/ˈdʌmˌæs//ˈdʌmˌæs/US informal stupid:
My dumb-ass brother lost my phone.
It was a dumb-ass mistake to make.
dumb-assnoun [ C ]
/ˈdʌmˌæs//ˈdʌmˌæs/US informal someone who is stupid:
Some dumb-ass left his keys in the front door.
Don't be a dumb-ass.