Definition of surface blow in English:
surface blow
noun
1Engineering
A device by which the surface water and scum in a steam boiler may be blown off.2A blow occurring when a whale is at the surface.
3Metallurgy
A defect in metal in the form of a small cavity on the surface of a casting.
Origin
Mid 19th century; earliest use found in United States Nautical Magazine & Naval Journal.
Are You Learning English? Here Are Our Top English Tips