diamond in the rough

Definition from Wiktionary, a free dictionary

[edit] English

[edit] Alternative forms

• rough diamond

[edit] Noun

diamond in the rough (plural diamonds in the rough)

1. An uncut diamond.
2. (idiomatic) A person whose goodness or other positive qualities are hidden by a harsh or unremarkable surface appearance.

   That auto mechanic is a diamond in the rough, tough-talking, but honest, even generous.