WordNet (r) 3.0 (2006):

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:
         blister rust, 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: blister rust, Cronartium ribicola]