Source : WordNet®

blister rust
     n 1: any of several diseases of pines caused by rust fungi of the
          genus Cronartium and marked by destructive invasion of
          bark and sapwood and producing blisters externally [syn:
           {white-pine rust}, {white pine blister rust}]
     2: fungus causing white pine blister rust and having a complex
        life cycle requiring a plant of genus Ribes as alternate
        host [syn: {Cronartium ribicola}]