as “meder omuraliev” has answered, you may use a more specified selector. and I would like to provider a general way that how to sepcific a higher priority for any type of selector, that is use the attr presdeo.

for example:

html body .foo { font-family: Arial !important;}
html body .bar[attr]{ font-family: Arial !important;}

to override this you may use like this:

html body .foo:not([NONE_EXISTS_ATTR]){ font-family: Consolas !important;}
html body .bar[attr]:not([NONE_EXISTS_ATTR]){ font-family: Consolas !important;}