I. ˈ ̷ ̷ˌ ̷ ̷ noun
Etymology: blue (I) + stone
1. : the hydrated copper sulfate CuSO 4 .5H 2 O
2. : a building or paving stone of bluish gray color ; specifically : a sandstone quarried near the Hudson river
II. transitive verb
: to treat (as a net or a stream) with copper sulfate