An archaic or dialectal term meaning to put something into or through a trough, or to form into a trough shape.
From en- (prefix meaning to put into) + trough (a long shallow container). This appears to be an obsolete English formation, likely regional or historical, combining common Old English word-building patterns.
Entrough is so archaic that it barely appears in modern dictionaries, but it's a perfect example of how English once had productive word-building rules where 'en-' could be added to almost any noun to create a verb!
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