
1) Arizona copse 2) Clump of trees in a prairie 3) Grove of prairie trees 4) Southwestern copse 5) Tree grove 6) Woody copse 
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https://www.crosswordclues.com/clue/motte

An earthwork mound topped with a tower or shell keep.
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http://great-castles.com/glossary.php

artificial mound upon which a castle is built
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http://phrontistery.info/m.html

• (n.) A clump of trees in a prairie.
Found on 
http://thinkexist.com/dictionary/meaning/motte/

(from the article `Europe, history of`) ...The decline of the popular courts and public jurisdiction had been accompanied by the appearance of innumerable private fortresses, often little ... ...social organization and warfare was the motte-and-bailey castle, which appeared in the 10th and 11th centuries between the Rhine and Loire rive...
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http://www.britannica.com/eb/a-z/m/128

artificial or improved natural mound on which castle was built
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http://www.castles-of-britain.com/glossary.htm

A mound of earth on which a tower was built; artificial conical earth mound (sometimes an old barrow) for the keep
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http://www.castlesontheweb.com/glossary.html

A mound of earth on which a tower was built; artificial conical earth mound (sometimes an old barrow) for the keep
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http://www.encyclo.co.uk/local/20018

Fortified mound within a castle or other fortification. At the Norman conquest, it was necessary to garrison the country at speed, and mottes, often surrounded only by ditches or wooden walls, were...
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http://www.encyclo.co.uk/local/20688

The first castles built by the Normans often consisted of a steep-sided earthen mound with a tower built on it. The mound was known as a motte. 
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http://www.encyclo.co.uk/local/20766

a steep sided mound surmounted by a keep or other defendable structure which formed the central feature of early castles. See fortification 
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http://www.encyclo.co.uk/local/20935

a mound, often man-made, on which a castle was built
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http://www.encyclo.co.uk/local/22129

Copse or small stand of trees on a prairie, such as the oak mottes found on the coastal prairie of eastern Texas.
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http://www.encyclo.co.uk/local/22218

Artificial mound.
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http://www.encyclo.co.uk/visitor-contributions.php
 Motte  noun
Motte  noun [ Confer French 
 motte a clod, clump, or hillock.] A clump of trees in a prairie. [ Local, U.S.]
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http://www.encyclo.co.uk/webster/M/107

a mound, often man-made, on which a castle was built
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https://www.encyclo.co.uk/local/20402

a grove or clump of trees in prairie land or open country.
Found on 
https://www.infoplease.com/dictionary/motte
  No exact match found.