Umhlaza wegazi, nokwabizwa ngokuba ngumhlaza wegazi, uqala kumongo wethambo, kulapho kuveliswa khona igazi. Umhlaza wegazi wenzeka xa iiseli zegazi ezingaqhelekanga ziqala ukukhula ngaphandle kolawulo, ziphazamisa ukusebenza kweeseli eziqhelekileyo zegazi, ezilwa nosulelo kwaye zivelise iiseli zegazi ezintsha.
