The Collaborative International Dictionary of English v.0.48:

lobster-backed \lobster-backed\ adj. (American History)
   Of or pertaining to British soldiers during the Revolutionary
   War in America; -- so called because of their red coats.

   Syn: red-coated.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

lobster-backed
    adj 1: used of British soldiers during the American
           Revolutionary War because of their red coats [syn: red-
           coated, lobster-backed]