As nouns the difference between blocage and blockage
is that blocage is the roughest and cheapest sort of rubblework, in masonry while blockage is the state of being blocked.
blocage
English
Noun
(
-)
(architecture) The roughest and cheapest sort of rubblework, in masonry.
(
Webster 1913)
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blockage
English
Noun
(
en noun)
The state of being blocked
A thing that is blocking
- There was a blockage in the sewer, so we called out the plumber.