The Collaborative International Dictionary of English v.0.48:

Thatcher \Thatch"er\, n.
   One who thatches.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Thatcher
    n 1: British stateswoman; first woman to serve as Prime Minister
         (born in 1925) [syn: Thatcher, Margaret Thatcher,
         Margaret Hilda Thatcher, Baroness Thatcher of Kesteven,
         Iron Lady]
    2: someone skilled in making a roof from plant stalks or foliage