Wordnet 3.0
NOUN (2)
1. 
 the condition of being coated or clogged with rust; 
2. 
 ineptitude or awkwardness as a consequence of age or lack of practice; 
- Example: "his rustiness showed when he was asked to speed up"
The Collaborative International Dictionary of English v.0.48:
Rustiness \Rust"i*ness\, n.
   The quality or state of being rusty.
   [1913 Webster]
WordNet (r) 3.0 (2006):
rustiness
    n 1: the condition of being coated or clogged with rust
    2: ineptitude or awkwardness as a consequence of age or lack of
       practice; "his rustiness showed when he was asked to speed
       up"