Grunge is a grimy, sooty, or otherwise dirty state. The grunge of a rented cabin might have you re-thinking your plans to camp there all weekend.
You may romanticize the idea of working on cars at a garage, including the grunge under your fingernails. Grunge is dirt and grime, or the condition of being covered in it. In the mid-1980s, the word was loaned to a new kind of underground music, and the style and culture surrounding it. Mark Arm, the lead singer for a Seattle band, is usually credited with coining this meaning of grunge when he wrote in a 1981 zine, "Pure grunge! Pure noise!"