The Collaborative International Dictionary of English v.0.48:

Undermanned \Un`der*manned"\, a. (Naut.)
   Insufficiently furnished with men; short-handed.
   [1913 Webster]

WordNet (r) 3.0 (2006):

undermanned
    adj 1: inadequate in number of workers or assistants etc.;
           "they're rather short-handed at the moment"; "overcrowded
           and understaffed hospitals" [syn: short-handed, short-
           staffed, undermanned, understaffed]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "undermanned":
   bare-handed, beggarly, empty-handed, famished, half-starved,
   ill off, ill-equipped, ill-furnished, ill-provided, impoverished,
   on short commons, pauperized, poor, shorthanded, starved,
   starveling, starving, underfed, underhanded, undernourished,
   understaffed, unfed, unprovided, unreplenished, unsupplied