Real Dictionary

dirt
A dirt road or track is made from hard earth. A dirt floor is made from earth without any cement, stone, or wood laid on it.
uncountable noun: If there is dirt on something, there is dust, mud, or a stain on it.
uncountable noun: You can refer to the earth on the ground as dirt, especially when it is dusty.

dirt in American English
any unclean or soiling matter, as mud, dust, dung, trash, etc.; filth
having a surface of compacted earth
noun: any foul or filthy substance, as mud, grime, dust, or excrement

dirt in British English
noun: any unclean substance, such as mud, dust, excrement, etc; filth