The Collaborative International Dictionary of English v.0.48:

dead beat \dead` beat"\ (d[e^]d`b[=e]t"), deadbeat
\dead"beat`\(d[e^]d"b[=e]t`).
   a loafer, sponger, or swindler; especially, one who does not
   pay his debts. Same as Beat, n., 7. [Low, U.S.]
   [1913 Webster]