/ ˈrʌsti; NAmE / adjective
1.
covered with rust :
rusty metal
a rusty old car
2.
[ not usually before noun ] ( informal ) ( of a sport, skill, etc. ) not as good as it used to be, because you have not been practising :
My tennis is very rusty these days.
I haven't played the piano for ages—I may be a little rusty.
► rusti·ness noun [ U ]
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WORD ORIGIN
Old English rūstig (see rust , -y ).