The Collaborative International Dictionary of English v.0.48:

Thatch \Thatch\, n. [OE. thak, AS. [thorn][ae]c a roof; akin to
   [thorn]eccean to cover, D. dak a roof, dekken to cover, G.
   dach a roof, decken 8cover, Icel. [thorn]ak a roof, Sw. tak,
   Dan. tag, Lith. st[=o]gas, Ir. teagh a house, Gael. teach,
   tigh, W. ty, L. tegere to cover, toga a toga, Gr. ?, ?, a
   roof, ? to cover, Skr. sthag. Cf. Deck, Integument,
   Tile, Toga.]
   1. Straw, rushes, or the like, used for making or covering
      the roofs of buildings, or of stacks of hay or grain.
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   2. (Bot.) A name in the West Indies for several kinds of
      palm, the leaves of which are used for thatching.
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   Thatch sparrow, the house sparrow. [Prov. Eng.]
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