Definition of nossir in US English:

nossir

(also nosir)

exclamation

North American
informal
  • Used emphatically: certainly not’; ‘indeed not’.

Origin

Early 20th century; earliest use found in The Fort Wayne Sentinel. Representing a colloquial pronunciation of no sir from no [interjection] + sir.

Pronunciation

nossir

/ˈnəʊˌsəː/