malingerer

[F. malingre sickly, weakly, prob. from mal ill + OF. heingre, haingre, thin, lean, infirm, fr. L. aeger.]
In the army, a soldier who feigns himself sick, or who induces or protracts an illness, in order to avoid doing his duty; hence, in general, one who shirks his duty by pretending illness or inability.

Employee who pretends to be ill so as to be relieved of work assignments or job responsibilities.

A Marine or recruit who spends too much time at sick call or makes other excuses to get out of training or duty. It is a punishable offense under the UCMJ.

The noun has one meaning:

Meaning #1: someone shirking their duty by feigning illness or incapacity
  Synonyms: skulker, shammer