What is obstructor?

Some articles on obstructor:

USS Obstructor (ACM-7)
... USS Obstructor (ACM-7) was a Chimo-class minelayer in the United States Navy during World War II ... The ship was transferred to the Navy, 4 January 1945 renamed Obstructor, 19 January 1945 converted at the Charleston Navy Yard and commissioned 1 April 1945, Lt ...

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